diff --git a/alethzero/MainWin.cpp b/alethzero/MainWin.cpp
index 2a66a6d69..04fc7757c 100644
--- a/alethzero/MainWin.cpp
+++ b/alethzero/MainWin.cpp
@@ -1626,7 +1626,7 @@ void Main::on_data_textChanged()
 			catch (dev::Exception const& exception)
 			{
 				ostringstream error;
-				solidity::SourceReferenceFormatter::printExceptionInformation(error, exception, "Error", compiler.getScanner());
+				solidity::SourceReferenceFormatter::printExceptionInformation(error, exception, "Error", compiler);
 				solidity = "<h4>Solidity</h4><pre>" + QString::fromStdString(error.str()).toHtmlEscaped() + "</pre>";
 			}
 			catch (...)
diff --git a/libsolidity/AST.cpp b/libsolidity/AST.cpp
index 4bd0b2c0e..697ffe8e3 100644
--- a/libsolidity/AST.cpp
+++ b/libsolidity/AST.cpp
@@ -33,6 +33,19 @@ namespace dev
 namespace solidity
 {
 
+void SourceUnit::accept(ASTVisitor& _visitor)
+{
+	if (_visitor.visit(*this))
+		listAccept(m_nodes, _visitor);
+	_visitor.endVisit(*this);
+}
+
+void ImportDirective::accept(ASTVisitor& _visitor)
+{
+	_visitor.visit(*this);
+	_visitor.endVisit(*this);
+}
+
 void ContractDefinition::accept(ASTVisitor& _visitor)
 {
 	if (_visitor.visit(*this))
@@ -57,34 +70,6 @@ void StructDefinition::checkValidityOfMembers()
 	checkRecursion();
 }
 
-void StructDefinition::checkMemberTypes()
-{
-	for (ASTPointer<VariableDeclaration> const& member: getMembers())
-		if (!member->getType()->canBeStored())
-			BOOST_THROW_EXCEPTION(member->createTypeError("Type cannot be used in struct."));
-}
-
-void StructDefinition::checkRecursion()
-{
-	set<StructDefinition const*> definitionsSeen;
-	vector<StructDefinition const*> queue = {this};
-	while (!queue.empty())
-	{
-		StructDefinition const* def = queue.back();
-		queue.pop_back();
-		if (definitionsSeen.count(def))
-			BOOST_THROW_EXCEPTION(ParserError() << errinfo_sourceLocation(def->getLocation())
-												<< errinfo_comment("Recursive struct definition."));
-		definitionsSeen.insert(def);
-		for (ASTPointer<VariableDeclaration> const& member: def->getMembers())
-			if (member->getType()->getCategory() == Type::Category::STRUCT)
-			{
-				UserDefinedTypeName const& typeName = dynamic_cast<UserDefinedTypeName&>(*member->getTypeName());
-				queue.push_back(&dynamic_cast<StructDefinition const&>(*typeName.getReferencedDeclaration()));
-			}
-	}
-}
-
 void ParameterList::accept(ASTVisitor& _visitor)
 {
 	if (_visitor.visit(*this))
@@ -312,6 +297,34 @@ vector<FunctionDefinition const*> ContractDefinition::getInterfaceFunctions() co
 	return exportedFunctions;
 }
 
+void StructDefinition::checkMemberTypes()
+{
+	for (ASTPointer<VariableDeclaration> const& member: getMembers())
+		if (!member->getType()->canBeStored())
+			BOOST_THROW_EXCEPTION(member->createTypeError("Type cannot be used in struct."));
+}
+
+void StructDefinition::checkRecursion()
+{
+	set<StructDefinition const*> definitionsSeen;
+	vector<StructDefinition const*> queue = {this};
+	while (!queue.empty())
+	{
+		StructDefinition const* def = queue.back();
+		queue.pop_back();
+		if (definitionsSeen.count(def))
+			BOOST_THROW_EXCEPTION(ParserError() << errinfo_sourceLocation(def->getLocation())
+												<< errinfo_comment("Recursive struct definition."));
+		definitionsSeen.insert(def);
+		for (ASTPointer<VariableDeclaration> const& member: def->getMembers())
+			if (member->getType()->getCategory() == Type::Category::STRUCT)
+			{
+				UserDefinedTypeName const& typeName = dynamic_cast<UserDefinedTypeName&>(*member->getTypeName());
+				queue.push_back(&dynamic_cast<StructDefinition const&>(*typeName.getReferencedDeclaration()));
+			}
+	}
+}
+
 void FunctionDefinition::checkTypeRequirements()
 {
 	for (ASTPointer<VariableDeclaration> const& var: getParameters() + getReturnParameters())
diff --git a/libsolidity/AST.h b/libsolidity/AST.h
index d29e84a0a..10616022b 100644
--- a/libsolidity/AST.h
+++ b/libsolidity/AST.h
@@ -79,6 +79,42 @@ private:
 	Location m_location;
 };
 
+/**
+ * Source unit containing import directives and contract definitions.
+ */
+class SourceUnit: public ASTNode
+{
+public:
+	SourceUnit(Location const& _location, std::vector<ASTPointer<ASTNode>> const& _nodes):
+		ASTNode(_location), m_nodes(_nodes) {}
+
+	virtual void accept(ASTVisitor& _visitor) override;
+
+	std::vector<ASTPointer<ASTNode>> getNodes() const { return m_nodes; }
+
+private:
+	std::vector<ASTPointer<ASTNode>> m_nodes;
+};
+
+/**
+ * Import directive for referencing other files / source objects.
+ * Example: import "abc.sol"
+ * Source objects are identified by a string which can be a file name but does not have to be.
+ */
+class ImportDirective: public ASTNode
+{
+public:
+	ImportDirective(Location const& _location, ASTPointer<ASTString> const& _identifier):
+		ASTNode(_location), m_identifier(_identifier) {}
+
+	virtual void accept(ASTVisitor& _visitor) override;
+
+	ASTString const& getIdentifier() const { return *m_identifier; }
+
+private:
+	ASTPointer<ASTString> m_identifier;
+};
+
 /**
  * Abstract AST class for a declaration (contract, function, struct, variable).
  */
diff --git a/libsolidity/ASTForward.h b/libsolidity/ASTForward.h
index a369c8a79..8b4bac1ce 100644
--- a/libsolidity/ASTForward.h
+++ b/libsolidity/ASTForward.h
@@ -34,6 +34,8 @@ namespace solidity
 {
 
 class ASTNode;
+class SourceUnit;
+class ImportDirective;
 class Declaration;
 class ContractDefinition;
 class StructDefinition;
diff --git a/libsolidity/ASTPrinter.cpp b/libsolidity/ASTPrinter.cpp
index 987ad11cc..3d09fd9af 100644
--- a/libsolidity/ASTPrinter.cpp
+++ b/libsolidity/ASTPrinter.cpp
@@ -43,6 +43,13 @@ void ASTPrinter::print(ostream& _stream)
 }
 
 
+bool ASTPrinter::visit(ImportDirective& _node)
+{
+	writeLine("ImportDirective \"" + _node.getIdentifier() + "\"");
+	printSourcePart(_node);
+	return goDeeper();
+}
+
 bool ASTPrinter::visit(ContractDefinition& _node)
 {
 	writeLine("ContractDefinition \"" + _node.getName() + "\"");
@@ -270,7 +277,7 @@ bool ASTPrinter::visit(Literal& _node)
 	return goDeeper();
 }
 
-void ASTPrinter::endVisit(ASTNode&)
+void ASTPrinter::endVisit(ImportDirective&)
 {
 	m_indentation--;
 }
diff --git a/libsolidity/ASTPrinter.h b/libsolidity/ASTPrinter.h
index e0757fbc4..1a18fc4a1 100644
--- a/libsolidity/ASTPrinter.h
+++ b/libsolidity/ASTPrinter.h
@@ -42,6 +42,7 @@ public:
 	/// Output the string representation of the AST to _stream.
 	void print(std::ostream& _stream);
 
+	bool visit(ImportDirective& _node) override;
 	bool visit(ContractDefinition& _node) override;
 	bool visit(StructDefinition& _node) override;
 	bool visit(ParameterList& _node) override;
@@ -73,7 +74,7 @@ public:
 	bool visit(ElementaryTypeNameExpression& _node) override;
 	bool visit(Literal& _node) override;
 
-	void endVisit(ASTNode& _node) override;
+	void endVisit(ImportDirective&) override;
 	void endVisit(ContractDefinition&) override;
 	void endVisit(StructDefinition&) override;
 	void endVisit(ParameterList&) override;
diff --git a/libsolidity/ASTVisitor.h b/libsolidity/ASTVisitor.h
index 6e579f358..bf1ccc410 100644
--- a/libsolidity/ASTVisitor.h
+++ b/libsolidity/ASTVisitor.h
@@ -42,6 +42,8 @@ class ASTVisitor
 {
 public:
 	virtual bool visit(ASTNode&) { return true; }
+	virtual bool visit(SourceUnit&) { return true; }
+	virtual bool visit(ImportDirective&) { return true; }
 	virtual bool visit(ContractDefinition&) { return true; }
 	virtual bool visit(StructDefinition&) { return true; }
 	virtual bool visit(ParameterList&) { return true; }
@@ -74,6 +76,8 @@ public:
 	virtual bool visit(Literal&) { return true; }
 
 	virtual void endVisit(ASTNode&) { }
+	virtual void endVisit(SourceUnit&) { }
+	virtual void endVisit(ImportDirective&) { }
 	virtual void endVisit(ContractDefinition&) { }
 	virtual void endVisit(StructDefinition&) { }
 	virtual void endVisit(ParameterList&) { }
diff --git a/libsolidity/BaseTypes.h b/libsolidity/BaseTypes.h
index d1ffd7bbc..a8fd77c86 100644
--- a/libsolidity/BaseTypes.h
+++ b/libsolidity/BaseTypes.h
@@ -22,6 +22,8 @@
 
 #pragma once
 
+#include <memory>
+#include <string>
 #include <ostream>
 
 namespace dev
@@ -35,19 +37,19 @@ namespace solidity
  */
 struct Location
 {
-	Location(int _start, int _end): start(_start), end(_end) { }
+	Location(int _start, int _end, std::shared_ptr<std::string const> _sourceName):
+		start(_start), end(_end), sourceName(_sourceName) { }
 	Location(): start(-1), end(-1) { }
 
-	bool IsValid() const { return start >= 0 && end >= start; }
-
 	int start;
 	int end;
+	std::shared_ptr<std::string const> sourceName;
 };
 
 /// Stream output for Location (used e.g. in boost exceptions).
 inline std::ostream& operator<<(std::ostream& _out, Location const& _location)
 {
-	return _out << "[" << _location.start << "," << _location.end << ")";
+	return _out << *_location.sourceName << "[" << _location.start << "," << _location.end << ")";
 }
 
 }
diff --git a/libsolidity/CompilerStack.cpp b/libsolidity/CompilerStack.cpp
index 01bf99d94..d0b1df181 100644
--- a/libsolidity/CompilerStack.cpp
+++ b/libsolidity/CompilerStack.cpp
@@ -36,22 +36,43 @@ namespace dev
 namespace solidity
 {
 
-CompilerStack::CompilerStack(): m_interfaceHandler(make_shared<InterfaceHandler>()) {}
+void CompilerStack::addSource(string const& _name, string const& _content)
+{
+	if (m_sources.count(_name))
+		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("Source by given name already exists."));
+
+	reset(true);
+	m_sources[_name].scanner = make_shared<Scanner>(CharStream(_content), _name);
+}
 
 void CompilerStack::setSource(string const& _sourceCode)
 {
 	reset();
-	m_scanner = make_shared<Scanner>(CharStream(_sourceCode));
+	addSource("", _sourceCode);
 }
 
 void CompilerStack::parse()
 {
-	if (!m_scanner)
-		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("Source not available."));
-	m_contractASTNode = Parser().parse(m_scanner);
+	for (auto& sourcePair: m_sources)
+	{
+		sourcePair.second.scanner->reset();
+		sourcePair.second.ast = Parser().parse(sourcePair.second.scanner);
+	}
+	resolveImports();
+
 	m_globalContext = make_shared<GlobalContext>();
-	m_globalContext->setCurrentContract(*m_contractASTNode);
-	NameAndTypeResolver(m_globalContext->getDeclarations()).resolveNamesAndTypes(*m_contractASTNode);
+	NameAndTypeResolver resolver(m_globalContext->getDeclarations());
+	for (Source const* source: m_sourceOrder)
+		resolver.registerDeclarations(*source->ast);
+	for (Source const* source: m_sourceOrder)
+		for (ASTPointer<ASTNode> const& node: source->ast->getNodes())
+			if (ContractDefinition* contract = dynamic_cast<ContractDefinition*>(node.get()))
+			{
+				m_globalContext->setCurrentContract(*contract);
+				resolver.updateDeclaration(*m_globalContext->getCurrentThis());
+				resolver.resolveNamesAndTypes(*contract);
+				m_contracts[contract->getName()].contract = contract;
+			}
 	m_parseSuccessful = true;
 }
 
@@ -61,54 +82,90 @@ void CompilerStack::parse(string const& _sourceCode)
 	parse();
 }
 
-bytes const& CompilerStack::compile(bool _optimize)
+vector<string> CompilerStack::getContractNames()
 {
 	if (!m_parseSuccessful)
 		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("Parsing was not successful."));
-	m_bytecode.clear();
-	m_compiler = make_shared<Compiler>();
-	m_compiler->compileContract(*m_contractASTNode, m_globalContext->getMagicVariables());
-	return m_bytecode = m_compiler->getAssembledBytecode(_optimize);
+	vector<string> contractNames;
+	for (auto const& contract: m_contracts)
+		contractNames.push_back(contract.first);
+	return contractNames;
+}
+
+void CompilerStack::compile(bool _optimize)
+{
+	if (!m_parseSuccessful)
+		parse();
+	for (Source const* source: m_sourceOrder)
+		for (ASTPointer<ASTNode> const& node: source->ast->getNodes())
+			if (ContractDefinition* contract = dynamic_cast<ContractDefinition*>(node.get()))
+			{
+				m_globalContext->setCurrentContract(*contract);
+				shared_ptr<Compiler> compiler = make_shared<Compiler>();
+				compiler->compileContract(*contract, m_globalContext->getMagicVariables());
+				Contract& compiledContract = m_contracts[contract->getName()];
+				compiledContract.bytecode = compiler->getAssembledBytecode(_optimize);
+				compiledContract.compiler = move(compiler);
+			}
 }
 
 bytes const& CompilerStack::compile(string const& _sourceCode, bool _optimize)
 {
 	parse(_sourceCode);
-	return compile(_optimize);
+	compile(_optimize);
+	return getBytecode();
 }
 
-void CompilerStack::streamAssembly(ostream& _outStream)
+bytes const& CompilerStack::getBytecode(string const& _contractName)
 {
-	if (!m_compiler || m_bytecode.empty())
-		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("Compilation was not successful."));
-	m_compiler->streamAssembly(_outStream);
+	return getContract(_contractName).bytecode;
 }
 
-std::string const& CompilerStack::getJsonDocumentation(DocumentationType _type)
+void CompilerStack::streamAssembly(ostream& _outStream, string const& _contractName)
+{
+	getContract(_contractName).compiler->streamAssembly(_outStream);
+}
+
+string const& CompilerStack::getInterface(std::string const& _contractName)
+{
+	return getJsonDocumentation(_contractName, ABI_INTERFACE);
+}
+
+std::string const& CompilerStack::getJsonDocumentation(std::string const& _contractName, DocumentationType _type)
 {
 	if (!m_parseSuccessful)
 		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("Parsing was not successful."));
 
-	auto createDocIfNotThere = [this, _type](std::unique_ptr<string>& _doc)
-	{
-		if (!_doc)
-			_doc = m_interfaceHandler->getDocumentation(m_contractASTNode, _type);
-	};
+	Contract& contract = getContract(_contractName);
 
+	std::unique_ptr<string>* doc;
 	switch (_type)
 	{
 	case DocumentationType::NATSPEC_USER:
-		createDocIfNotThere(m_userDocumentation);
-		return *m_userDocumentation;
+		doc = &contract.userDocumentation;
+		break;
 	case DocumentationType::NATSPEC_DEV:
-		createDocIfNotThere(m_devDocumentation);
-		return *m_devDocumentation;
+		doc = &contract.devDocumentation;
+		break;
 	case DocumentationType::ABI_INTERFACE:
-		createDocIfNotThere(m_interface);
-		return *m_interface;
+		doc = &contract.interface;
+		break;
+	default:
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Illegal documentation type."));
 	}
+	if (!*doc)
+		*doc = contract.interfaceHandler->getDocumentation(*contract.contract, _type);
+	return *(*doc);
+}
 
-	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Illegal documentation type."));
+Scanner const& CompilerStack::getScanner(string const& _sourceName)
+{
+	return *getSource(_sourceName).scanner;
+}
+
+SourceUnit& CompilerStack::getAST(string const& _sourceName)
+{
+	return *getSource(_sourceName).ast;
 }
 
 bytes CompilerStack::staticCompile(std::string const& _sourceCode, bool _optimize)
@@ -117,7 +174,70 @@ bytes CompilerStack::staticCompile(std::string const& _sourceCode, bool _optimiz
 	return stack.compile(_sourceCode, _optimize);
 }
 
+void CompilerStack::reset(bool _keepSources)
+{
+	m_parseSuccessful = false;
+	if (_keepSources)
+		for (auto sourcePair: m_sources)
+			sourcePair.second.reset();
+	else
+		m_sources.clear();
+	m_globalContext.reset();
+	m_sourceOrder.clear();
+	m_contracts.clear();
+}
+
+void CompilerStack::resolveImports()
+{
+	// topological sorting (depth first search) of the import graph, cutting potential cycles
+	vector<Source const*> sourceOrder;
+	set<Source const*> sourcesSeen;
+
+	function<void(Source const*)> toposort = [&](Source const* _source)
+	{
+		if (sourcesSeen.count(_source))
+			return;
+		sourcesSeen.insert(_source);
+		for (ASTPointer<ASTNode> const& node: _source->ast->getNodes())
+			if (ImportDirective const* import = dynamic_cast<ImportDirective*>(node.get()))
+			{
+				string const& id = import->getIdentifier();
+				if (!m_sources.count(id))
+					BOOST_THROW_EXCEPTION(ParserError()
+										  << errinfo_sourceLocation(import->getLocation())
+										  << errinfo_comment("Source not found."));
+				toposort(&m_sources[id]);
+			}
+		sourceOrder.push_back(_source);
+	};
+
+	for (auto const& sourcePair: m_sources)
+		toposort(&sourcePair.second);
+
+	swap(m_sourceOrder, sourceOrder);
+}
+
+CompilerStack::Contract& CompilerStack::getContract(string const& _contractName)
+{
+	if (m_contracts.empty())
+		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("No compiled contracts found."));
+	if (_contractName.empty())
+		return m_contracts.begin()->second;
+	auto it = m_contracts.find(_contractName);
+	if (it == m_contracts.end())
+		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("Contract " + _contractName + " not found."));
+	return it->second;
+}
+
+CompilerStack::Source& CompilerStack::getSource(string const& _sourceName)
+{
+	auto it = m_sources.find(_sourceName);
+	if (it == m_sources.end())
+		BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("Given source file not found."));
+	return it->second;
+}
 
+CompilerStack::Contract::Contract(): interfaceHandler(make_shared<InterfaceHandler>()) {}
 
 }
 }
diff --git a/libsolidity/CompilerStack.h b/libsolidity/CompilerStack.h
index 928815cc5..82d275498 100644
--- a/libsolidity/CompilerStack.h
+++ b/libsolidity/CompilerStack.h
@@ -25,6 +25,7 @@
 #include <ostream>
 #include <string>
 #include <memory>
+#include <boost/noncopyable.hpp>
 #include <libdevcore/Common.h>
 
 namespace dev {
@@ -33,6 +34,7 @@ namespace solidity {
 // forward declarations
 class Scanner;
 class ContractDefinition;
+class SourceUnit;
 class Compiler;
 class GlobalContext;
 class InterfaceHandler;
@@ -49,52 +51,85 @@ enum class DocumentationType: uint8_t
  * It holds state and can be used to either step through the compilation stages (and abort e.g.
  * before compilation to bytecode) or run the whole compilation in one call.
  */
-class CompilerStack
+class CompilerStack: boost::noncopyable
 {
 public:
-	CompilerStack();
-	void reset() {  *this = CompilerStack(); }
+	CompilerStack(): m_parseSuccessful(false) {}
+
+	/// Adds a source object (e.g. file) to the parser. After this, parse has to be called again.
+	void addSource(std::string const& _name, std::string const& _content);
 	void setSource(std::string const& _sourceCode);
+	/// Parses all source units that were added
 	void parse();
+	/// Sets the given source code as the only source unit and parses it.
 	void parse(std::string const& _sourceCode);
-	/// Compiles the contract that was previously parsed.
-	bytes const& compile(bool _optimize = false);
+	/// Returns a list of the contract names in the sources.
+	std::vector<std::string> getContractNames();
+
+	/// Compiles the source units that were previously added and parsed.
+	void compile(bool _optimize = false);
 	/// Parses and compiles the given source code.
+	/// @returns the compiled bytecode
 	bytes const& compile(std::string const& _sourceCode, bool _optimize = false);
 
-	bytes const& getBytecode() const { return m_bytecode; }
+	bytes const& getBytecode(std::string const& _contractName = "");
 	/// Streams a verbose version of the assembly to @a _outStream.
 	/// Prerequisite: Successful compilation.
-	void streamAssembly(std::ostream& _outStream);
+	void streamAssembly(std::ostream& _outStream, std::string const& _contractName = "");
 
 	/// Returns a string representing the contract interface in JSON.
 	/// Prerequisite: Successful call to parse or compile.
-	std::string const& getInterface();
+	std::string const& getInterface(std::string const& _contractName = "");
 	/// Returns a string representing the contract's documentation in JSON.
 	/// Prerequisite: Successful call to parse or compile.
 	/// @param type The type of the documentation to get.
-	/// Can be one of 3 types defined at @c documentation_type
-	std::string const& getJsonDocumentation(DocumentationType type);
+	/// Can be one of 3 types defined at @c DocumentationType
+	std::string const& getJsonDocumentation(std::string const& _contractName, DocumentationType _type);
 
 	/// Returns the previously used scanner, useful for counting lines during error reporting.
-	Scanner const& getScanner() const { return *m_scanner; }
-	ContractDefinition& getAST() const { return *m_contractASTNode; }
+	Scanner const& getScanner(std::string const& _sourceName = "");
+	SourceUnit& getAST(std::string const& _sourceName = "");
 
 	/// Compile the given @a _sourceCode to bytecode. If a scanner is provided, it is used for
 	/// scanning the source code - this is useful for printing exception information.
 	static bytes staticCompile(std::string const& _sourceCode, bool _optimize = false);
 
 private:
-	std::shared_ptr<Scanner> m_scanner;
-	std::shared_ptr<GlobalContext> m_globalContext;
-	std::shared_ptr<ContractDefinition> m_contractASTNode;
+	/**
+	 * Information pertaining to one source unit, filled gradually during parsing and compilation.
+	 */
+	struct Source
+	{
+		std::shared_ptr<Scanner> scanner;
+		std::shared_ptr<SourceUnit> ast;
+		std::string interface;
+		void reset() { scanner.reset(); ast.reset(); interface.clear(); }
+	};
+
+	struct Contract
+	{
+		ContractDefinition* contract;
+		std::shared_ptr<Compiler> compiler;
+		bytes bytecode;
+		std::shared_ptr<InterfaceHandler> interfaceHandler;
+		std::unique_ptr<std::string> interface;
+		std::unique_ptr<std::string> userDocumentation;
+		std::unique_ptr<std::string> devDocumentation;
+
+		Contract();
+	};
+
+	void reset(bool _keepSources = false);
+	void resolveImports();
+
+	Contract& getContract(std::string const& _contractName = "");
+	Source& getSource(std::string const& _sourceName = "");
+
 	bool m_parseSuccessful;
-	std::unique_ptr<std::string> m_interface;
-	std::unique_ptr<std::string> m_userDocumentation;
-	std::unique_ptr<std::string> m_devDocumentation;
-	std::shared_ptr<Compiler> m_compiler;
-	std::shared_ptr<InterfaceHandler> m_interfaceHandler;
-	bytes m_bytecode;
+	std::map<std::string, Source> m_sources;
+	std::shared_ptr<GlobalContext> m_globalContext;
+	std::vector<Source const*> m_sourceOrder;
+	std::map<std::string, Contract> m_contracts;
 };
 
 }
diff --git a/libsolidity/DeclarationContainer.cpp b/libsolidity/DeclarationContainer.cpp
index 6ea9c28c5..c0dea757a 100644
--- a/libsolidity/DeclarationContainer.cpp
+++ b/libsolidity/DeclarationContainer.cpp
@@ -28,9 +28,9 @@ namespace dev
 namespace solidity
 {
 
-bool DeclarationContainer::registerDeclaration(Declaration& _declaration)
+bool DeclarationContainer::registerDeclaration(Declaration& _declaration, bool _update)
 {
-	if (m_declarations.find(_declaration.getName()) != m_declarations.end())
+	if (!_update && m_declarations.find(_declaration.getName()) != m_declarations.end())
 		return false;
 	m_declarations[_declaration.getName()] = &_declaration;
 	return true;
diff --git a/libsolidity/DeclarationContainer.h b/libsolidity/DeclarationContainer.h
index db6812890..e1b363e04 100644
--- a/libsolidity/DeclarationContainer.h
+++ b/libsolidity/DeclarationContainer.h
@@ -43,7 +43,7 @@ public:
 		m_enclosingDeclaration(_enclosingDeclaration), m_enclosingContainer(_enclosingContainer) {}
 	/// Registers the declaration in the scope unless its name is already declared. Returns true iff
 	/// it was not yet declared.
-	bool registerDeclaration(Declaration& _declaration);
+	bool registerDeclaration(Declaration& _declaration, bool _update = false);
 	Declaration* resolveName(ASTString const& _name, bool _recursive = false) const;
 	Declaration* getEnclosingDeclaration() const { return m_enclosingDeclaration; }
 
diff --git a/libsolidity/Exceptions.h b/libsolidity/Exceptions.h
index 8298c9810..14f919772 100644
--- a/libsolidity/Exceptions.h
+++ b/libsolidity/Exceptions.h
@@ -38,7 +38,6 @@ struct CompilerError: virtual Exception {};
 struct InternalCompilerError: virtual Exception {};
 struct DocstringParsingError: virtual Exception {};
 
-typedef boost::error_info<struct tag_sourcePosition, int> errinfo_sourcePosition;
 typedef boost::error_info<struct tag_sourceLocation, Location> errinfo_sourceLocation;
 
 }
diff --git a/libsolidity/GlobalContext.cpp b/libsolidity/GlobalContext.cpp
index d8b637076..45242bb1f 100644
--- a/libsolidity/GlobalContext.cpp
+++ b/libsolidity/GlobalContext.cpp
@@ -74,11 +74,10 @@ vector<Declaration*> GlobalContext::getDeclarations() const
 	declarations.reserve(m_magicVariables.size() + 1);
 	for (ASTPointer<Declaration> const& variable: m_magicVariables)
 		declarations.push_back(variable.get());
-	declarations.push_back(getCurrentThis());
 	return declarations;
 }
 
-MagicVariableDeclaration*GlobalContext::getCurrentThis() const
+MagicVariableDeclaration* GlobalContext::getCurrentThis() const
 {
 	if (!m_thisPointer[m_currentContract])
 		m_thisPointer[m_currentContract] = make_shared<MagicVariableDeclaration>(
diff --git a/libsolidity/GlobalContext.h b/libsolidity/GlobalContext.h
index 0166734ca..ddbd049c2 100644
--- a/libsolidity/GlobalContext.h
+++ b/libsolidity/GlobalContext.h
@@ -47,12 +47,14 @@ class GlobalContext: private boost::noncopyable
 public:
 	GlobalContext();
 	void setCurrentContract(ContractDefinition const& _contract);
+	MagicVariableDeclaration* getCurrentThis() const;
 
+	/// @returns all magic variables.
 	std::vector<MagicVariableDeclaration const*> getMagicVariables() const;
+	/// @returns a vector of all implicit global declarations excluding "this".
 	std::vector<Declaration*> getDeclarations() const;
 
 private:
-	MagicVariableDeclaration* getCurrentThis() const;
 	std::vector<std::shared_ptr<MagicVariableDeclaration>> m_magicVariables;
 	ContractDefinition const* m_currentContract;
 	std::map<ContractDefinition const*, std::shared_ptr<MagicVariableDeclaration>> mutable m_thisPointer;
diff --git a/libsolidity/InterfaceHandler.cpp b/libsolidity/InterfaceHandler.cpp
index 18c053cb1..c3e62cad0 100644
--- a/libsolidity/InterfaceHandler.cpp
+++ b/libsolidity/InterfaceHandler.cpp
@@ -15,7 +15,7 @@ InterfaceHandler::InterfaceHandler()
 	m_lastTag = DocTagType::NONE;
 }
 
-std::unique_ptr<std::string> InterfaceHandler::getDocumentation(std::shared_ptr<ContractDefinition> _contractDef,
+std::unique_ptr<std::string> InterfaceHandler::getDocumentation(ContractDefinition& _contractDef,
 																DocumentationType _type)
 {
 	switch(_type)
@@ -32,11 +32,11 @@ std::unique_ptr<std::string> InterfaceHandler::getDocumentation(std::shared_ptr<
 	return nullptr;
 }
 
-std::unique_ptr<std::string> InterfaceHandler::getABIInterface(std::shared_ptr<ContractDefinition> _contractDef)
+std::unique_ptr<std::string> InterfaceHandler::getABIInterface(ContractDefinition& _contractDef)
 {
 	Json::Value methods(Json::arrayValue);
 
-	for (FunctionDefinition const* f: _contractDef->getInterfaceFunctions())
+	for (FunctionDefinition const* f: _contractDef.getInterfaceFunctions())
 	{
 		Json::Value method;
 		Json::Value inputs(Json::arrayValue);
@@ -63,12 +63,12 @@ std::unique_ptr<std::string> InterfaceHandler::getABIInterface(std::shared_ptr<C
 	return std::unique_ptr<std::string>(new std::string(m_writer.write(methods)));
 }
 
-std::unique_ptr<std::string> InterfaceHandler::getUserDocumentation(std::shared_ptr<ContractDefinition> _contractDef)
+std::unique_ptr<std::string> InterfaceHandler::getUserDocumentation(ContractDefinition& _contractDef)
 {
 	Json::Value doc;
 	Json::Value methods(Json::objectValue);
 
-	for (FunctionDefinition const* f: _contractDef->getInterfaceFunctions())
+	for (FunctionDefinition const* f: _contractDef.getInterfaceFunctions())
 	{
 		Json::Value user;
 		auto strPtr = f->getDocumentation();
@@ -88,14 +88,14 @@ std::unique_ptr<std::string> InterfaceHandler::getUserDocumentation(std::shared_
 	return std::unique_ptr<std::string>(new std::string(m_writer.write(doc)));
 }
 
-std::unique_ptr<std::string> InterfaceHandler::getDevDocumentation(std::shared_ptr<ContractDefinition> _contractDef)
+std::unique_ptr<std::string> InterfaceHandler::getDevDocumentation(ContractDefinition& _contractDef)
 {
 	// LTODO: Somewhere in this function warnings for mismatch of param names
 	// should be thrown
 	Json::Value doc;
 	Json::Value methods(Json::objectValue);
 
-	for (FunctionDefinition const* f: _contractDef->getInterfaceFunctions())
+	for (FunctionDefinition const* f: _contractDef.getInterfaceFunctions())
 	{
 		Json::Value method;
 		auto strPtr = f->getDocumentation();
diff --git a/libsolidity/InterfaceHandler.h b/libsolidity/InterfaceHandler.h
index 524e2903c..e6be9e6a7 100644
--- a/libsolidity/InterfaceHandler.h
+++ b/libsolidity/InterfaceHandler.h
@@ -59,23 +59,23 @@ public:
 	///                     types provided by @c DocumentationType
 	/// @return             A unique pointer contained string with the json
 	///                     representation of provided type
-	std::unique_ptr<std::string> getDocumentation(std::shared_ptr<ContractDefinition> _contractDef,
+	std::unique_ptr<std::string> getDocumentation(ContractDefinition& _contractDef,
 												  DocumentationType _type);
 	/// Get the ABI Interface of the contract
 	/// @param _contractDef The contract definition
 	/// @return             A unique pointer contained string with the json
 	///                     representation of the contract's ABI Interface
-	std::unique_ptr<std::string> getABIInterface(std::shared_ptr<ContractDefinition> _contractDef);
+	std::unique_ptr<std::string> getABIInterface(ContractDefinition& _contractDef);
 	/// Get the User documentation of the contract
 	/// @param _contractDef The contract definition
 	/// @return             A unique pointer contained string with the json
 	///                     representation of the contract's user documentation
-	std::unique_ptr<std::string> getUserDocumentation(std::shared_ptr<ContractDefinition> _contractDef);
+	std::unique_ptr<std::string> getUserDocumentation(ContractDefinition& _contractDef);
 	/// Get the Developer's documentation of the contract
 	/// @param _contractDef The contract definition
 	/// @return             A unique pointer contained string with the json
 	///                     representation of the contract's developer documentation
-	std::unique_ptr<std::string> getDevDocumentation(std::shared_ptr<ContractDefinition> _contractDef);
+	std::unique_ptr<std::string> getDevDocumentation(ContractDefinition& _contractDef);
 
 private:
 	void resetUser();
diff --git a/libsolidity/NameAndTypeResolver.cpp b/libsolidity/NameAndTypeResolver.cpp
index d473348b8..3715df6ad 100644
--- a/libsolidity/NameAndTypeResolver.cpp
+++ b/libsolidity/NameAndTypeResolver.cpp
@@ -38,9 +38,14 @@ NameAndTypeResolver::NameAndTypeResolver(std::vector<Declaration*> const& _globa
 		m_scopes[nullptr].registerDeclaration(*declaration);
 }
 
+void NameAndTypeResolver::registerDeclarations(SourceUnit& _sourceUnit)
+{
+	// The helper registers all declarations in m_scopes as a side-effect of its construction.
+	DeclarationRegistrationHelper registrar(m_scopes, _sourceUnit);
+}
+
 void NameAndTypeResolver::resolveNamesAndTypes(ContractDefinition& _contract)
 {
-	DeclarationRegistrationHelper registrar(m_scopes, _contract);
 	m_currentScope = &m_scopes[&_contract];
 	for (ASTPointer<StructDefinition> const& structDef: _contract.getDefinedStructs())
 		ReferencesResolver resolver(*structDef, *this, nullptr);
@@ -65,6 +70,12 @@ void NameAndTypeResolver::resolveNamesAndTypes(ContractDefinition& _contract)
 	m_currentScope = &m_scopes[nullptr];
 }
 
+void NameAndTypeResolver::updateDeclaration(Declaration& _declaration)
+{
+	m_scopes[nullptr].registerDeclaration(_declaration, true);
+	_declaration.setScope(nullptr);
+}
+
 Declaration* NameAndTypeResolver::resolveName(ASTString const& _name, Declaration const* _scope) const
 {
 	auto iterator = m_scopes.find(_scope);
diff --git a/libsolidity/NameAndTypeResolver.h b/libsolidity/NameAndTypeResolver.h
index 797eca605..816d8006f 100644
--- a/libsolidity/NameAndTypeResolver.h
+++ b/libsolidity/NameAndTypeResolver.h
@@ -42,7 +42,13 @@ class NameAndTypeResolver: private boost::noncopyable
 {
 public:
 	explicit NameAndTypeResolver(std::vector<Declaration*> const& _globals);
+	/// Registers all declarations found in the source unit.
+	void registerDeclarations(SourceUnit& _sourceUnit);
+	/// Resolves all names and types referenced from the given contract.
 	void resolveNamesAndTypes(ContractDefinition& _contract);
+	/// Updates the given global declaration (used for "this"). Not to be used with declarations
+	/// that create their own scope.
+	void updateDeclaration(Declaration& _declaration);
 
 	/// Resolves the given @a _name inside the scope @a _scope. If @a _scope is omitted,
 	/// the global scope is used (i.e. the one containing only the contract).
diff --git a/libsolidity/Parser.cpp b/libsolidity/Parser.cpp
index 0506bc3e3..ddab489b6 100644
--- a/libsolidity/Parser.cpp
+++ b/libsolidity/Parser.cpp
@@ -20,30 +20,27 @@
  * Solidity parser.
  */
 
+#include <vector>
 #include <libdevcore/Log.h>
 #include <libsolidity/BaseTypes.h>
 #include <libsolidity/Parser.h>
 #include <libsolidity/Scanner.h>
 #include <libsolidity/Exceptions.h>
 
+using namespace std;
+
 namespace dev
 {
 namespace solidity
 {
 
-ASTPointer<ContractDefinition> Parser::parse(std::shared_ptr<Scanner> const& _scanner)
-{
-	m_scanner = _scanner;
-	return parseContractDefinition();
-}
-
-
 /// AST node factory that also tracks the begin and end position of an AST node
 /// while it is being parsed
 class Parser::ASTNodeFactory
 {
 public:
-	ASTNodeFactory(Parser const& _parser): m_parser(_parser), m_location(_parser.getPosition(), -1) {}
+	ASTNodeFactory(Parser const& _parser):
+		m_parser(_parser), m_location(_parser.getPosition(), -1, _parser.getSourceName()) {}
 
 	void markEndPosition() { m_location.end = m_parser.getEndPosition(); }
 	void setLocationEmpty() { m_location.end = m_location.start; }
@@ -55,7 +52,7 @@ public:
 	{
 		if (m_location.end < 0)
 			markEndPosition();
-		return std::make_shared<NodeType>(m_location, std::forward<Args>(_args)...);
+		return make_shared<NodeType>(m_location, forward<Args>(_args)...);
 	}
 
 private:
@@ -63,6 +60,33 @@ private:
 	Location m_location;
 };
 
+ASTPointer<SourceUnit> Parser::parse(shared_ptr<Scanner> const& _scanner)
+{
+	m_scanner = _scanner;
+	ASTNodeFactory nodeFactory(*this);
+	vector<ASTPointer<ASTNode>> nodes;
+	while (_scanner->getCurrentToken() != Token::EOS)
+	{
+		switch (m_scanner->getCurrentToken())
+		{
+		case Token::IMPORT:
+			nodes.push_back(parseImportDirective());
+			break;
+		case Token::CONTRACT:
+			nodes.push_back(parseContractDefinition());
+			break;
+		default:
+			BOOST_THROW_EXCEPTION(createParserError(std::string("Expected import directive or contract definition.")));
+		}
+	}
+	return nodeFactory.createNode<SourceUnit>(nodes);
+}
+
+std::shared_ptr<const string> const& Parser::getSourceName() const
+{
+	return m_scanner->getSourceName();
+}
+
 int Parser::getPosition() const
 {
 	return m_scanner->getCurrentLocation().start;
@@ -73,15 +97,27 @@ int Parser::getEndPosition() const
 	return m_scanner->getCurrentLocation().end;
 }
 
+ASTPointer<ImportDirective> Parser::parseImportDirective()
+{
+	ASTNodeFactory nodeFactory(*this);
+	expectToken(Token::IMPORT);
+	if (m_scanner->getCurrentToken() != Token::STRING_LITERAL)
+		BOOST_THROW_EXCEPTION(createParserError("Expected string literal (URL)."));
+	ASTPointer<ASTString> url = getLiteralAndAdvance();
+	nodeFactory.markEndPosition();
+	expectToken(Token::SEMICOLON);
+	return nodeFactory.createNode<ImportDirective>(url);
+}
+
 ASTPointer<ContractDefinition> Parser::parseContractDefinition()
 {
 	ASTNodeFactory nodeFactory(*this);
 	expectToken(Token::CONTRACT);
 	ASTPointer<ASTString> name = expectIdentifierToken();
 	expectToken(Token::LBRACE);
-	std::vector<ASTPointer<StructDefinition>> structs;
-	std::vector<ASTPointer<VariableDeclaration>> stateVariables;
-	std::vector<ASTPointer<FunctionDefinition>> functions;
+	vector<ASTPointer<StructDefinition>> structs;
+	vector<ASTPointer<VariableDeclaration>> stateVariables;
+	vector<ASTPointer<FunctionDefinition>> functions;
 	bool visibilityIsPublic = true;
 	while (true)
 	{
@@ -110,7 +146,6 @@ ASTPointer<ContractDefinition> Parser::parseContractDefinition()
 	}
 	nodeFactory.markEndPosition();
 	expectToken(Token::RBRACE);
-	expectToken(Token::EOS);
 	return nodeFactory.createNode<ContractDefinition>(name, structs, stateVariables, functions);
 }
 
@@ -119,7 +154,7 @@ ASTPointer<FunctionDefinition> Parser::parseFunctionDefinition(bool _isPublic)
 	ASTNodeFactory nodeFactory(*this);
 	ASTPointer<ASTString> docstring;
 	if (m_scanner->getCurrentCommentLiteral() != "")
-		docstring = std::make_shared<ASTString>(m_scanner->getCurrentCommentLiteral());
+		docstring = make_shared<ASTString>(m_scanner->getCurrentCommentLiteral());
 
 	expectToken(Token::FUNCTION);
 	ASTPointer<ASTString> name(expectIdentifierToken());
@@ -142,7 +177,7 @@ ASTPointer<FunctionDefinition> Parser::parseFunctionDefinition(bool _isPublic)
 		// create an empty parameter list at a zero-length location
 		ASTNodeFactory nodeFactory(*this);
 		nodeFactory.setLocationEmpty();
-		returnParameters = nodeFactory.createNode<ParameterList>(std::vector<ASTPointer<VariableDeclaration>>());
+		returnParameters = nodeFactory.createNode<ParameterList>(vector<ASTPointer<VariableDeclaration>>());
 	}
 	ASTPointer<Block> block = parseBlock();
 	nodeFactory.setEndPositionFromNode(block);
@@ -156,7 +191,7 @@ ASTPointer<StructDefinition> Parser::parseStructDefinition()
 	ASTNodeFactory nodeFactory(*this);
 	expectToken(Token::STRUCT);
 	ASTPointer<ASTString> name = expectIdentifierToken();
-	std::vector<ASTPointer<VariableDeclaration>> members;
+	vector<ASTPointer<VariableDeclaration>> members;
 	expectToken(Token::LBRACE);
 	while (m_scanner->getCurrentToken() != Token::RBRACE)
 	{
@@ -228,7 +263,7 @@ ASTPointer<Mapping> Parser::parseMapping()
 ASTPointer<ParameterList> Parser::parseParameterList(bool _allowEmpty)
 {
 	ASTNodeFactory nodeFactory(*this);
-	std::vector<ASTPointer<VariableDeclaration>> parameters;
+	vector<ASTPointer<VariableDeclaration>> parameters;
 	expectToken(Token::LPAREN);
 	if (!_allowEmpty || m_scanner->getCurrentToken() != Token::RPAREN)
 	{
@@ -249,7 +284,7 @@ ASTPointer<Block> Parser::parseBlock()
 {
 	ASTNodeFactory nodeFactory(*this);
 	expectToken(Token::LBRACE);
-	std::vector<ASTPointer<Statement>> statements;
+	vector<ASTPointer<Statement>> statements;
 	while (m_scanner->getCurrentToken() != Token::RBRACE)
 		statements.push_back(parseStatement());
 	nodeFactory.markEndPosition();
@@ -447,7 +482,7 @@ ASTPointer<Expression> Parser::parseLeftHandSideExpression()
 		case Token::LPAREN:
 		{
 			m_scanner->next();
-			std::vector<ASTPointer<Expression>> arguments = parseFunctionCallArguments();
+			vector<ASTPointer<Expression>> arguments = parseFunctionCallArguments();
 			nodeFactory.markEndPosition();
 			expectToken(Token::RPAREN);
 			expression = nodeFactory.createNode<FunctionCall>(expression, arguments);
@@ -503,9 +538,9 @@ ASTPointer<Expression> Parser::parsePrimaryExpression()
 	return expression;
 }
 
-std::vector<ASTPointer<Expression>> Parser::parseFunctionCallArguments()
+vector<ASTPointer<Expression>> Parser::parseFunctionCallArguments()
 {
-	std::vector<ASTPointer<Expression>> arguments;
+	vector<ASTPointer<Expression>> arguments;
 	if (m_scanner->getCurrentToken() != Token::RPAREN)
 	{
 		arguments.push_back(parseExpression());
@@ -521,7 +556,7 @@ std::vector<ASTPointer<Expression>> Parser::parseFunctionCallArguments()
 void Parser::expectToken(Token::Value _value)
 {
 	if (m_scanner->getCurrentToken() != _value)
-		BOOST_THROW_EXCEPTION(createParserError(std::string("Expected token ") + std::string(Token::getName(_value))));
+		BOOST_THROW_EXCEPTION(createParserError(string("Expected token ") + string(Token::getName(_value))));
 	m_scanner->next();
 }
 
@@ -543,14 +578,15 @@ ASTPointer<ASTString> Parser::expectIdentifierToken()
 
 ASTPointer<ASTString> Parser::getLiteralAndAdvance()
 {
-	ASTPointer<ASTString> identifier = std::make_shared<ASTString>(m_scanner->getCurrentLiteral());
+	ASTPointer<ASTString> identifier = make_shared<ASTString>(m_scanner->getCurrentLiteral());
 	m_scanner->next();
 	return identifier;
 }
 
-ParserError Parser::createParserError(std::string const& _description) const
+ParserError Parser::createParserError(string const& _description) const
 {
-	return ParserError() << errinfo_sourcePosition(getPosition()) << errinfo_comment(_description);
+	return ParserError() << errinfo_sourceLocation(Location(getPosition(), getPosition(), getSourceName()))
+						 << errinfo_comment(_description);
 }
 
 
diff --git a/libsolidity/Parser.h b/libsolidity/Parser.h
index 307a0d6a1..52a374e03 100644
--- a/libsolidity/Parser.h
+++ b/libsolidity/Parser.h
@@ -34,7 +34,8 @@ class Scanner;
 class Parser
 {
 public:
-	ASTPointer<ContractDefinition> parse(std::shared_ptr<Scanner> const& _scanner);
+	ASTPointer<SourceUnit> parse(std::shared_ptr<Scanner> const& _scanner);
+	std::shared_ptr<std::string const> const& getSourceName() const;
 
 private:
 	class ASTNodeFactory;
@@ -46,6 +47,7 @@ private:
 
 	///@{
 	///@name Parsing functions for the AST nodes
+	ASTPointer<ImportDirective> parseImportDirective();
 	ASTPointer<ContractDefinition> parseContractDefinition();
 	ASTPointer<FunctionDefinition> parseFunctionDefinition(bool _isPublic);
 	ASTPointer<StructDefinition> parseStructDefinition();
diff --git a/libsolidity/Scanner.cpp b/libsolidity/Scanner.cpp
index 2f5f8d37a..08bf744d4 100644
--- a/libsolidity/Scanner.cpp
+++ b/libsolidity/Scanner.cpp
@@ -143,17 +143,22 @@ private:
 }; // end of LiteralScope class
 
 
-void Scanner::reset(CharStream const& _source)
+void Scanner::reset(CharStream const& _source, string const& _sourceName)
 {
 	m_source = _source;
+	m_sourceName = make_shared<string const>(_sourceName);
+	reset();
+}
+
+void Scanner::reset()
+{
+	m_source.reset();
 	m_char = m_source.get();
 	skipWhitespace();
 	scanToken();
-
 	next();
 }
 
-
 bool Scanner::scanHexByte(char& o_scannedByte)
 {
 	char x = 0;
diff --git a/libsolidity/Scanner.h b/libsolidity/Scanner.h
index 49ac3651c..18b1f5d3a 100644
--- a/libsolidity/Scanner.h
+++ b/libsolidity/Scanner.h
@@ -79,6 +79,8 @@ public:
 	char advanceAndGet(size_t _chars=1);
 	char rollback(size_t _amount);
 
+	void reset() { m_pos = 0; }
+
 	///@{
 	///@name Error printing helper functions
 	/// Functions that help pretty-printing parse errors
@@ -99,11 +101,12 @@ class Scanner
 	friend class LiteralScope;
 public:
 
-	Scanner() { reset(CharStream()); }
-	explicit Scanner(CharStream const& _source) { reset(_source); }
+	explicit Scanner(CharStream const& _source = CharStream(), std::string const& _sourceName = "") { reset(_source, _sourceName); }
 
-	/// Resets the scanner as if newly constructed with _input as input.
-	void reset(CharStream const& _source);
+	/// Resets the scanner as if newly constructed with _source and _sourceName as input.
+	void reset(CharStream const& _source, std::string const& _sourceName);
+	/// Resets scanner to the start of input.
+	void reset();
 
 	/// Returns the next token and advances input
 	Token::Value next();
@@ -139,6 +142,8 @@ public:
 	std::string const& peekLiteral() const { return m_nextToken.literal; }
 	///@}
 
+	std::shared_ptr<std::string const> const& getSourceName() const { return m_sourceName; }
+
 	///@{
 	///@name Error printing helper functions
 	/// Functions that help pretty-printing parse errors
@@ -203,6 +208,7 @@ private:
 	TokenDesc m_nextToken;     // desc for next token (one token look-ahead)
 
 	CharStream m_source;
+	std::shared_ptr<std::string const> m_sourceName;
 
 	/// one character look-ahead, equals 0 at end of input
 	char m_char;
diff --git a/libsolidity/SourceReferenceFormatter.cpp b/libsolidity/SourceReferenceFormatter.cpp
index d3f2152a6..1a7d12a95 100644
--- a/libsolidity/SourceReferenceFormatter.cpp
+++ b/libsolidity/SourceReferenceFormatter.cpp
@@ -21,6 +21,7 @@
  */
 
 #include <libsolidity/SourceReferenceFormatter.h>
+#include <libsolidity/CompilerStack.h>
 #include <libsolidity/Scanner.h>
 #include <libsolidity/Exceptions.h>
 
@@ -38,7 +39,6 @@ void SourceReferenceFormatter::printSourceLocation(ostream& _stream,
 	int startLine;
 	int startColumn;
 	tie(startLine, startColumn) = _scanner.translatePositionToLineColumn(_location.start);
-	_stream << "starting at line " << (startLine + 1) << ", column " << (startColumn + 1) << "\n";
 	int endLine;
 	int endColumn;
 	tie(endLine, endColumn) = _scanner.translatePositionToLineColumn(_location.end);
@@ -58,37 +58,28 @@ void SourceReferenceFormatter::printSourceLocation(ostream& _stream,
 				<< "Spanning multiple lines.\n";
 }
 
-void SourceReferenceFormatter::printSourcePosition(ostream& _stream,
-												   int _position,
-												   const Scanner& _scanner)
-{
-	int line;
-	int column;
-	tie(line, column) = _scanner.translatePositionToLineColumn(_position);
-	_stream << "at line " << (line + 1) << ", column " << (column + 1) << endl
-			<< _scanner.getLineAtPosition(_position) << endl
-			<< string(column, ' ') << "^" << endl;
-}
-
 void SourceReferenceFormatter::printExceptionInformation(ostream& _stream,
 														 Exception const& _exception,
 														 string const& _name,
-														 Scanner const& _scanner)
+														 CompilerStack& _compiler)
 {
-	_stream << _name;
-	if (string const* description = boost::get_error_info<errinfo_comment>(_exception))
-		_stream << ": " << *description;
+	Location const* location = boost::get_error_info<errinfo_sourceLocation>(_exception);
+	Scanner const* scanner;
 
-	if (int const* position = boost::get_error_info<errinfo_sourcePosition>(_exception))
+	if (location)
 	{
-		_stream << " ";
-		printSourcePosition(_stream, *position, _scanner);
-	}
-	if (Location const* location = boost::get_error_info<errinfo_sourceLocation>(_exception))
-	{
-		_stream << " ";
-		printSourceLocation(_stream, *location, _scanner);
+		scanner = &_compiler.getScanner(*location->sourceName);
+		int startLine;
+		int startColumn;
+		tie(startLine, startColumn) = scanner->translatePositionToLineColumn(location->start);
+		_stream << *location->sourceName << ":" << (startLine + 1) << ":" << (startColumn + 1) << ": ";
 	}
+	_stream << _name;
+	if (string const* description = boost::get_error_info<errinfo_comment>(_exception))
+		_stream << ": " << *description << endl;
+
+	if (location)
+		printSourceLocation(_stream, *location, *scanner);
 }
 
 }
diff --git a/libsolidity/SourceReferenceFormatter.h b/libsolidity/SourceReferenceFormatter.h
index 4736066fd..9b5567045 100644
--- a/libsolidity/SourceReferenceFormatter.h
+++ b/libsolidity/SourceReferenceFormatter.h
@@ -34,14 +34,14 @@ namespace solidity
 {
 
 class Scanner; // forward
+class CompilerStack; // forward
 
 struct SourceReferenceFormatter
 {
 public:
 	static void printSourceLocation(std::ostream& _stream, Location const& _location, Scanner const& _scanner);
-	static void printSourcePosition(std::ostream& _stream, int _position, Scanner const& _scanner);
 	static void printExceptionInformation(std::ostream& _stream, Exception const& _exception,
-										  std::string const& _name, Scanner const& _scanner);
+										  std::string const& _name, CompilerStack& _compiler);
 };
 
 }
diff --git a/libweb3jsonrpc/WebThreeStubServer.cpp b/libweb3jsonrpc/WebThreeStubServer.cpp
index 7607b7a95..84a0ae42a 100644
--- a/libweb3jsonrpc/WebThreeStubServer.cpp
+++ b/libweb3jsonrpc/WebThreeStubServer.cpp
@@ -510,7 +510,7 @@ std::string WebThreeStubServer::eth_solidity(std::string const& _code)
 	catch (dev::Exception const& exception)
 	{
 		ostringstream error;
-		solidity::SourceReferenceFormatter::printExceptionInformation(error, exception, "Error", compiler.getScanner());
+		solidity::SourceReferenceFormatter::printExceptionInformation(error, exception, "Error", compiler);
 		cwarn << "Solidity compilation error: " << error.str();
 	}
 	catch (...)
diff --git a/mix/ConstantCompilationModel.cpp b/mix/ConstantCompilationModel.cpp
index e06734f59..ea12a267c 100644
--- a/mix/ConstantCompilationModel.cpp
+++ b/mix/ConstantCompilationModel.cpp
@@ -46,7 +46,7 @@ CompilerResult ConstantCompilationModel::compile(QString _code)
 	catch (dev::Exception const& _exception)
 	{
 		ostringstream error;
-		solidity::SourceReferenceFormatter::printExceptionInformation(error, _exception, "Error", compiler.getScanner());
+		solidity::SourceReferenceFormatter::printExceptionInformation(error, _exception, "Error", compiler);
 		res.success = false;
 		res.comment = QString::fromStdString(error.str()).toHtmlEscaped();
 		res.hexCode = "";
diff --git a/solc/main.cpp b/solc/main.cpp
index 21ffc98cc..61f73b45d 100644
--- a/solc/main.cpp
+++ b/solc/main.cpp
@@ -59,7 +59,7 @@ void version()
 
 int main(int argc, char** argv)
 {
-	string infile;
+	vector<string> infiles;
 	bool optimize = false;
 	for (int i = 1; i < argc; ++i)
 	{
@@ -71,49 +71,52 @@ int main(int argc, char** argv)
 		else if (arg == "-V" || arg == "--version")
 			version();
 		else
-			infile = argv[i];
+			infiles.push_back(argv[i]);
 	}
-	string sourceCode;
-	if (infile.empty())
+	map<string, string> sourceCodes;
+	if (infiles.empty())
 	{
 		string s;
 		while (!cin.eof())
 		{
 			getline(cin, s);
-			sourceCode.append(s);
+			sourceCodes["<stdin>"].append(s);
 		}
 	}
 	else
-		sourceCode = asString(dev::contents(infile));
+		for (string const& infile: infiles)
+			sourceCodes[infile] = asString(dev::contents(infile));
 
 	CompilerStack compiler;
 	try
 	{
-		compiler.compile(sourceCode, optimize);
+		for (auto const& sourceCode: sourceCodes)
+			compiler.addSource(sourceCode.first, sourceCode.second);
+		compiler.compile(optimize);
 	}
 	catch (ParserError const& exception)
 	{
-		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Parser error", compiler.getScanner());
+		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Parser error", compiler);
 		return -1;
 	}
 	catch (DeclarationError const& exception)
 	{
-		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Declaration error", compiler.getScanner());
+		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Declaration error", compiler);
 		return -1;
 	}
 	catch (TypeError const& exception)
 	{
-		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Type error", compiler.getScanner());
+		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Type error", compiler);
 		return -1;
 	}
 	catch (CompilerError const& exception)
 	{
-		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Compiler error", compiler.getScanner());
+		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Compiler error", compiler);
 		return -1;
 	}
 	catch (InternalCompilerError const& exception)
 	{
-		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Internal compiler error", compiler.getScanner());
+		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Internal compiler error", compiler);
 		return -1;
 	}
 	catch (Exception const& exception)
@@ -127,17 +130,27 @@ int main(int argc, char** argv)
 		return -1;
 	}
 
-	cout << "Syntax tree for the contract:" << endl;
-	ASTPrinter printer(compiler.getAST(), sourceCode);
-	printer.print(cout);
-	cout << "EVM assembly:" << endl;
-	compiler.streamAssembly(cout);
-	cout << "Opcodes:" << endl;
-	cout << eth::disassemble(compiler.getBytecode()) << endl;
-	cout << "Binary: " << toHex(compiler.getBytecode()) << endl;
-	cout << "Interface specification: " << compiler.getJsonDocumentation(DocumentationType::ABI_INTERFACE) << endl;
-	cout << "Natspec user documentation: " << compiler.getJsonDocumentation(DocumentationType::NATSPEC_USER) << endl;
-	cout << "Natspec developer documentation: " << compiler.getJsonDocumentation(DocumentationType::NATSPEC_DEV) << endl;
+	cout << "Syntax trees:" << endl << endl;
+	for (auto const& sourceCode: sourceCodes)
+	{
+		cout << endl << "======= " << sourceCode.first << " =======" << endl;
+		ASTPrinter printer(compiler.getAST(sourceCode.first), sourceCode.second);
+		printer.print(cout);
+	}
+	vector<string> contracts = compiler.getContractNames();
+	cout << endl << "Contracts:" << endl;
+	for (string const& contract: contracts)
+	{
+		cout << endl << "======= " << contract << " =======" << endl
+			 << "EVM assembly:" << endl;
+		compiler.streamAssembly(cout, contract);
+		cout << "Opcodes:" << endl
+			 << eth::disassemble(compiler.getBytecode(contract)) << endl
+			 << "Binary: " << toHex(compiler.getBytecode(contract)) << endl
+			 << "Interface specification: " << compiler.getJsonDocumentation(contract, DocumentationType::ABI_INTERFACE) << endl
+			 << "Natspec user documentation: " << compiler.getJsonDocumentation(contract, DocumentationType::NATSPEC_USER) << endl
+			 << "Natspec developer documentation: " << compiler.getJsonDocumentation(contract, DocumentationType::NATSPEC_DEV) << endl;
+	}
 
 	return 0;
 }
diff --git a/test/solidityCompiler.cpp b/test/solidityCompiler.cpp
index 3e86919a6..9862cba83 100644
--- a/test/solidityCompiler.cpp
+++ b/test/solidityCompiler.cpp
@@ -46,16 +46,23 @@ namespace
 bytes compileContract(const string& _sourceCode)
 {
 	Parser parser;
-	ASTPointer<ContractDefinition> contract;
-	BOOST_REQUIRE_NO_THROW(contract = parser.parse(make_shared<Scanner>(CharStream(_sourceCode))));
+	ASTPointer<SourceUnit> sourceUnit;
+	BOOST_REQUIRE_NO_THROW(sourceUnit = parser.parse(make_shared<Scanner>(CharStream(_sourceCode))));
 	NameAndTypeResolver resolver({});
-	BOOST_REQUIRE_NO_THROW(resolver.resolveNamesAndTypes(*contract));
-
-	Compiler compiler;
-	compiler.compileContract(*contract, {});
-	// debug
-	//compiler.streamAssembly(cout);
-	return compiler.getAssembledBytecode();
+	resolver.registerDeclarations(*sourceUnit);
+	for (ASTPointer<ASTNode> const& node: sourceUnit->getNodes())
+		if (ContractDefinition* contract = dynamic_cast<ContractDefinition*>(node.get()))
+		{
+			BOOST_REQUIRE_NO_THROW(resolver.resolveNamesAndTypes(*contract));
+
+			Compiler compiler;
+			compiler.compileContract(*contract, {});
+			// debug
+			//compiler.streamAssembly(cout);
+			return compiler.getAssembledBytecode();
+		}
+	BOOST_FAIL("No contract found in source.");
+	return bytes();
 }
 
 /// Checks that @a _compiledCode is present starting from offset @a _offset in @a _expectation.
diff --git a/test/solidityExpressionCompiler.cpp b/test/solidityExpressionCompiler.cpp
index 6ea66badb..486b46ebb 100644
--- a/test/solidityExpressionCompiler.cpp
+++ b/test/solidityExpressionCompiler.cpp
@@ -86,27 +86,34 @@ bytes compileFirstExpression(const string& _sourceCode, vector<vector<string>> _
 							 vector<vector<string>> _localVariables = {})
 {
 	Parser parser;
-	ASTPointer<ContractDefinition> contract;
-	BOOST_REQUIRE_NO_THROW(contract = parser.parse(make_shared<Scanner>(CharStream(_sourceCode))));
+	ASTPointer<SourceUnit> sourceUnit;
+	BOOST_REQUIRE_NO_THROW(sourceUnit = parser.parse(make_shared<Scanner>(CharStream(_sourceCode))));
 	NameAndTypeResolver resolver({});
-	BOOST_REQUIRE_NO_THROW(resolver.resolveNamesAndTypes(*contract));
-	FirstExpressionExtractor extractor(*contract);
-	BOOST_REQUIRE(extractor.getExpression() != nullptr);
-
-	CompilerContext context;
-	for (vector<string> const& function: _functions)
-		context.addFunction(dynamic_cast<FunctionDefinition const&>(resolveDeclaration(function, resolver)));
-	for (vector<string> const& variable: _localVariables)
-		context.addVariable(dynamic_cast<VariableDeclaration const&>(resolveDeclaration(variable, resolver)));
-
-	ExpressionCompiler::compileExpression(context, *extractor.getExpression());
-
-	for (vector<string> const& function: _functions)
-		context << context.getFunctionEntryLabel(dynamic_cast<FunctionDefinition const&>(resolveDeclaration(function, resolver)));
-	bytes instructions = context.getAssembledBytecode();
-	// debug
-	// cout << eth::disassemble(instructions) << endl;
-	return instructions;
+	resolver.registerDeclarations(*sourceUnit);
+	for (ASTPointer<ASTNode> const& node: sourceUnit->getNodes())
+		if (ContractDefinition* contract = dynamic_cast<ContractDefinition*>(node.get()))
+		{
+			BOOST_REQUIRE_NO_THROW(resolver.resolveNamesAndTypes(*contract));
+			FirstExpressionExtractor extractor(*contract);
+			BOOST_REQUIRE(extractor.getExpression() != nullptr);
+
+			CompilerContext context;
+			for (vector<string> const& function: _functions)
+				context.addFunction(dynamic_cast<FunctionDefinition const&>(resolveDeclaration(function, resolver)));
+			for (vector<string> const& variable: _localVariables)
+				context.addVariable(dynamic_cast<VariableDeclaration const&>(resolveDeclaration(variable, resolver)));
+
+			ExpressionCompiler::compileExpression(context, *extractor.getExpression());
+
+			for (vector<string> const& function: _functions)
+				context << context.getFunctionEntryLabel(dynamic_cast<FunctionDefinition const&>(resolveDeclaration(function, resolver)));
+			bytes instructions = context.getAssembledBytecode();
+			// debug
+			// cout << eth::disassemble(instructions) << endl;
+			return instructions;
+		}
+	BOOST_FAIL("No contract found in source.");
+	return bytes();
 }
 
 } // end anonymous namespace
diff --git a/test/solidityJSONInterfaceTest.cpp b/test/solidityJSONInterfaceTest.cpp
index 17e97dc69..487508bb9 100644
--- a/test/solidityJSONInterfaceTest.cpp
+++ b/test/solidityJSONInterfaceTest.cpp
@@ -50,7 +50,7 @@ public:
 				msg += *extra;
 			BOOST_FAIL(msg);
 		}
-		std::string generatedInterfaceString = m_compilerStack.getJsonDocumentation(DocumentationType::ABI_INTERFACE);
+		std::string generatedInterfaceString = m_compilerStack.getJsonDocumentation("", DocumentationType::ABI_INTERFACE);
 		Json::Value generatedInterface;
 		m_reader.parse(generatedInterfaceString, generatedInterface);
 		Json::Value expectedInterface;
diff --git a/test/solidityNameAndTypeResolution.cpp b/test/solidityNameAndTypeResolution.cpp
index 8804c519c..783972296 100644
--- a/test/solidityNameAndTypeResolution.cpp
+++ b/test/solidityNameAndTypeResolution.cpp
@@ -41,10 +41,12 @@ namespace
 void parseTextAndResolveNames(std::string const& _source)
 {
 	Parser parser;
-	ASTPointer<ContractDefinition> contract = parser.parse(
-										   std::make_shared<Scanner>(CharStream(_source)));
+	ASTPointer<SourceUnit> sourceUnit = parser.parse(std::make_shared<Scanner>(CharStream(_source)));
 	NameAndTypeResolver resolver({});
-	resolver.resolveNamesAndTypes(*contract);
+	resolver.registerDeclarations(*sourceUnit);
+	for (ASTPointer<ASTNode> const& node: sourceUnit->getNodes())
+		if (ContractDefinition* contract = dynamic_cast<ContractDefinition*>(node.get()))
+			resolver.resolveNamesAndTypes(*contract);
 }
 }
 
diff --git a/test/solidityNatspecJSON.cpp b/test/solidityNatspecJSON.cpp
index 5e4c1fca7..f1795fe1c 100644
--- a/test/solidityNatspecJSON.cpp
+++ b/test/solidityNatspecJSON.cpp
@@ -55,9 +55,9 @@ public:
 		}
 
 		if (_userDocumentation)
-			generatedDocumentationString = m_compilerStack.getJsonDocumentation(DocumentationType::NATSPEC_USER);
+			generatedDocumentationString = m_compilerStack.getJsonDocumentation("", DocumentationType::NATSPEC_USER);
 		else
-			generatedDocumentationString = m_compilerStack.getJsonDocumentation(DocumentationType::NATSPEC_DEV);
+			generatedDocumentationString = m_compilerStack.getJsonDocumentation("", DocumentationType::NATSPEC_DEV);
 		Json::Value generatedDocumentation;
 		m_reader.parse(generatedDocumentationString, generatedDocumentation);
 		Json::Value expectedDocumentation;
diff --git a/test/solidityParser.cpp b/test/solidityParser.cpp
index 6a97a5d99..a9e2d531f 100644
--- a/test/solidityParser.cpp
+++ b/test/solidityParser.cpp
@@ -21,13 +21,15 @@
  */
 
 #include <string>
-
+#include <memory>
 #include <libdevcore/Log.h>
 #include <libsolidity/Scanner.h>
 #include <libsolidity/Parser.h>
 #include <libsolidity/Exceptions.h>
 #include <boost/test/unit_test.hpp>
 
+using namespace std;
+
 namespace dev
 {
 namespace solidity
@@ -40,7 +42,12 @@ namespace
 ASTPointer<ContractDefinition> parseText(std::string const& _source)
 {
 	Parser parser;
-	return parser.parse(std::make_shared<Scanner>(CharStream(_source)));
+	ASTPointer<SourceUnit> sourceUnit = parser.parse(std::make_shared<Scanner>(CharStream(_source)));
+	for (ASTPointer<ASTNode> const& node: sourceUnit->getNodes())
+		if (ASTPointer<ContractDefinition> contract = dynamic_pointer_cast<ContractDefinition>(node))
+			return contract;
+	BOOST_FAIL("No contract found in source.");
+	return ASTPointer<ContractDefinition>();
 }
 }
 
@@ -380,6 +387,50 @@ BOOST_AUTO_TEST_CASE(statement_starting_with_type_conversion)
 	BOOST_CHECK_NO_THROW(parseText(text));
 }
 
+BOOST_AUTO_TEST_CASE(import_directive)
+{
+	char const* text = "import \"abc\";\n"
+					   "contract test {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n";
+	BOOST_CHECK_NO_THROW(parseText(text));
+}
+
+BOOST_AUTO_TEST_CASE(multiple_contracts)
+{
+	char const* text = "contract test {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n"
+					   "contract test2 {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n";
+	BOOST_CHECK_NO_THROW(parseText(text));
+}
+
+BOOST_AUTO_TEST_CASE(multiple_contracts_and_imports)
+{
+	char const* text = "import \"abc\";\n"
+					   "contract test {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n"
+					   "import \"def\";\n"
+					   "contract test2 {\n"
+					   "  function fun() {\n"
+					   "    uint64(2);\n"
+					   "  }\n"
+					   "}\n"
+					   "import \"ghi\";\n";
+	BOOST_CHECK_NO_THROW(parseText(text));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }