diff --git a/libsolidity/AST.cpp b/libsolidity/AST.cpp
index 70af8f98e..d5f856dfc 100644
--- a/libsolidity/AST.cpp
+++ b/libsolidity/AST.cpp
@@ -278,6 +278,15 @@ vector<FunctionDefinition const*> ContractDefinition::getInterfaceFunctions() co
 	return exportedFunctions;
 }
 
+void FunctionDefinition::checkTypeRequirements()
+{
+	for (ASTPointer<VariableDeclaration> const& var: getParameters() + getReturnParameters())
+		if (!var->getType()->canLiveOutsideStorage())
+			BOOST_THROW_EXCEPTION(var->createTypeError("Type is required to live outside storage."));
+
+	m_body->checkTypeRequirements();
+}
+
 void Block::checkTypeRequirements()
 {
 	for (shared_ptr<Statement> const& statement: m_statements)
@@ -315,7 +324,7 @@ void Return::checkTypeRequirements()
 void VariableDefinition::checkTypeRequirements()
 {
 	// Variables can be declared without type (with "var"), in which case the first assignment
-	// setsthe type.
+	// sets the type.
 	// Note that assignments before the first declaration are legal because of the special scoping
 	// rules inherited from JavaScript.
 	if (m_value)
@@ -329,13 +338,14 @@ void VariableDefinition::checkTypeRequirements()
 			m_variable->setType(m_value->getType());
 		}
 	}
+	if (m_variable->getType() && !m_variable->getType()->canLiveOutsideStorage())
+		BOOST_THROW_EXCEPTION(m_variable->createTypeError("Type is required to live outside storage."));
 }
 
 void Assignment::checkTypeRequirements()
 {
 	m_leftHandSide->checkTypeRequirements();
-	if (!m_leftHandSide->isLvalue())
-		BOOST_THROW_EXCEPTION(createTypeError("Expression has to be an lvalue."));
+	m_leftHandSide->requireLValue();
 	m_rightHandSide->expectType(*m_leftHandSide->getType());
 	m_type = m_leftHandSide->getType();
 	if (m_assigmentOperator != Token::ASSIGN)
@@ -359,13 +369,19 @@ void Expression::expectType(Type const& _expectedType)
 											  + _expectedType.toString() + "."));
 }
 
+void Expression::requireLValue()
+{
+	if (!isLvalue())
+		BOOST_THROW_EXCEPTION(createTypeError("Expression has to be an lvalue."));
+	m_lvalueRequested = true;
+}
+
 void UnaryOperation::checkTypeRequirements()
 {
 	// INC, DEC, ADD, SUB, NOT, BIT_NOT, DELETE
 	m_subExpression->checkTypeRequirements();
 	if (m_operator == Token::Value::INC || m_operator == Token::Value::DEC || m_operator == Token::Value::DELETE)
-		if (!m_subExpression->isLvalue())
-			BOOST_THROW_EXCEPTION(createTypeError("Expression has to be an lvalue."));
+		m_subExpression->requireLValue();
 	m_type = m_subExpression->getType();
 	if (!m_type->acceptsUnaryOperator(m_operator))
 		BOOST_THROW_EXCEPTION(createTypeError("Unary operator not compatible with type."));
@@ -416,6 +432,8 @@ void FunctionCall::checkTypeRequirements()
 	}
 	else
 	{
+		m_expression->requireLValue();
+
 		//@todo would be nice to create a struct type from the arguments
 		// and then ask if that is implicitly convertible to the struct represented by the
 		// function parameters
@@ -448,8 +466,15 @@ void MemberAccess::checkTypeRequirements()
 
 void IndexAccess::checkTypeRequirements()
 {
-	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Index access not yet implemented."));
-	// m_type = ;
+	m_base->checkTypeRequirements();
+	m_base->requireLValue();
+	if (m_base->getType()->getCategory() != Type::Category::MAPPING)
+		BOOST_THROW_EXCEPTION(m_base->createTypeError("Indexed expression has to be a mapping (is " +
+													  m_base->getType()->toString() + ")"));
+	MappingType const& type = dynamic_cast<MappingType const&>(*m_base->getType());
+	m_index->expectType(*type.getKeyType());
+	m_type = type.getValueType();
+	m_isLvalue = true;
 }
 
 void Identifier::checkTypeRequirements()
@@ -481,6 +506,7 @@ void Identifier::checkTypeRequirements()
 		// Calling a function (e.g. function(12), otherContract.function(34)) does not do a type
 		// conversion.
 		m_type = make_shared<FunctionType>(*functionDef);
+		m_isLvalue = true;
 		return;
 	}
 	ContractDefinition* contractDef = dynamic_cast<ContractDefinition*>(m_referencedDeclaration);
diff --git a/libsolidity/AST.h b/libsolidity/AST.h
index 7b266f132..31ca56f76 100644
--- a/libsolidity/AST.h
+++ b/libsolidity/AST.h
@@ -186,6 +186,8 @@ public:
 	void addLocalVariable(VariableDeclaration const& _localVariable) { m_localVariables.push_back(&_localVariable); }
 	std::vector<VariableDeclaration const*> const& getLocalVariables() const { return m_localVariables; }
 
+	/// Checks that all parameters have allowed types and calls checkTypeRequirements on the body.
+	void checkTypeRequirements();
 private:
 	bool m_isPublic;
 	ASTPointer<ParameterList> m_parameters;
@@ -236,7 +238,7 @@ public:
 
 	/// Retrieve the element of the type hierarchy this node refers to. Can return an empty shared
 	/// pointer until the types have been resolved using the @ref NameAndTypeResolver.
-	virtual std::shared_ptr<Type> toType() = 0;
+	virtual std::shared_ptr<Type> toType() const = 0;
 };
 
 /**
@@ -252,7 +254,7 @@ public:
 		if (asserts(Token::isElementaryTypeName(_type))) BOOST_THROW_EXCEPTION(InternalCompilerError());
 	}
 	virtual void accept(ASTVisitor& _visitor) override;
-	virtual std::shared_ptr<Type> toType() override { return Type::fromElementaryTypeName(m_type); }
+	virtual std::shared_ptr<Type> toType() const override { return Type::fromElementaryTypeName(m_type); }
 
 	Token::Value getTypeName() const { return m_type; }
 
@@ -270,7 +272,7 @@ public:
 	UserDefinedTypeName(Location const& _location, ASTPointer<ASTString> const& _name):
 		TypeName(_location), m_name(_name) {}
 	virtual void accept(ASTVisitor& _visitor) override;
-	virtual std::shared_ptr<Type> toType() override { return Type::fromUserDefinedTypeName(*this); }
+	virtual std::shared_ptr<Type> toType() const override { return Type::fromUserDefinedTypeName(*this); }
 
 	ASTString const& getName() const { return *m_name; }
 	void setReferencedStruct(StructDefinition& _referencedStruct) { m_referencedStruct = &_referencedStruct; }
@@ -292,7 +294,10 @@ public:
 			ASTPointer<TypeName> const& _valueType):
 		TypeName(_location), m_keyType(_keyType), m_valueType(_valueType) {}
 	virtual void accept(ASTVisitor& _visitor) override;
-	virtual std::shared_ptr<Type> toType() override { return Type::fromMapping(*this); }
+	virtual std::shared_ptr<Type> toType() const override { return Type::fromMapping(*this); }
+
+	ElementaryTypeName const& getKeyType() const { return *m_keyType; }
+	TypeName const& getValueType() const { return *m_valueType; }
 
 private:
 	ASTPointer<ElementaryTypeName> m_keyType;
@@ -481,7 +486,7 @@ private:
 class Expression: public ASTNode
 {
 public:
-	Expression(Location const& _location): ASTNode(_location), m_isLvalue(false) {}
+	Expression(Location const& _location): ASTNode(_location), m_isLvalue(false), m_lvalueRequested(false) {}
 	virtual void checkTypeRequirements() = 0;
 
 	std::shared_ptr<Type const> const& getType() const { return m_type; }
@@ -490,6 +495,12 @@ public:
 	/// Helper function, infer the type via @ref checkTypeRequirements and then check that it
 	/// is implicitly convertible to @a _expectedType. If not, throw exception.
 	void expectType(Type const& _expectedType);
+	/// Checks that this expression is an lvalue and also registers that an address and
+	/// not a value is generated during compilation. Can be called after checkTypeRequirements()
+	/// by an enclosing expression.
+	void requireLValue();
+	/// Returns true if @a requireLValue was previously called on this expression.
+	bool lvalueRequested() const { return m_lvalueRequested; }
 
 protected:
 	//! Inferred type of the expression, only filled after a call to checkTypeRequirements().
@@ -497,6 +508,8 @@ protected:
 	//! Whether or not this expression is an lvalue, i.e. something that can be assigned to.
 	//! This is set during calls to @a checkTypeRequirements()
 	bool m_isLvalue;
+	//! Whether the outer expression requested the address (true) or the value (false) of this expression.
+	bool m_lvalueRequested;
 };
 
 /// Assignment, can also be a compound assignment.
@@ -543,6 +556,7 @@ public:
 
 	Token::Value getOperator() const { return m_operator; }
 	bool isPrefixOperation() const { return m_isPrefix; }
+	Expression& getSubExpression() const { return *m_subExpression; }
 
 private:
 	Token::Value m_operator;
@@ -635,6 +649,8 @@ public:
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void checkTypeRequirements() override;
 
+	Expression& getBaseExpression() const { return *m_base; }
+	Expression& getIndexExpression() const { return *m_index; }
 private:
 	ASTPointer<Expression> m_base;
 	ASTPointer<Expression> m_index;
diff --git a/libsolidity/Compiler.cpp b/libsolidity/Compiler.cpp
index da28ba8a3..eed886783 100644
--- a/libsolidity/Compiler.cpp
+++ b/libsolidity/Compiler.cpp
@@ -225,7 +225,7 @@ bool Compiler::visit(IfStatement& _ifStatement)
 	eth::AssemblyItem trueTag = m_context.appendConditionalJump();
 	if (_ifStatement.getFalseStatement())
 		_ifStatement.getFalseStatement()->accept(*this);
-	eth::AssemblyItem endTag = m_context.appendJump();
+	eth::AssemblyItem endTag = m_context.appendJumpToNew();
 	m_context << trueTag;
 	_ifStatement.getTrueStatement().accept(*this);
 	m_context << endTag;
diff --git a/libsolidity/CompilerContext.h b/libsolidity/CompilerContext.h
index 562c29321..e624222dd 100644
--- a/libsolidity/CompilerContext.h
+++ b/libsolidity/CompilerContext.h
@@ -65,7 +65,9 @@ public:
 	/// Appends a JUMPI instruction to @a _tag
 	CompilerContext& appendConditionalJumpTo(eth::AssemblyItem const& _tag) { m_asm.appendJumpI(_tag); return *this; }
 	/// Appends a JUMP to a new tag and @returns the tag
-	eth::AssemblyItem appendJump() { return m_asm.appendJump().tag(); }
+	eth::AssemblyItem appendJumpToNew() { return m_asm.appendJump().tag(); }
+	/// Appends a JUMP to a tag already on the stack
+	CompilerContext&  appendJump() { return *this << eth::Instruction::JUMP; }
 	/// Appends a JUMP to a specific tag
 	CompilerContext& appendJumpTo(eth::AssemblyItem const& _tag) { m_asm.appendJump(_tag); return *this; }
 	/// Appends pushing of a new tag and @returns the new tag.
diff --git a/libsolidity/ExpressionCompiler.cpp b/libsolidity/ExpressionCompiler.cpp
index 05bbb0916..d80b42b35 100644
--- a/libsolidity/ExpressionCompiler.cpp
+++ b/libsolidity/ExpressionCompiler.cpp
@@ -22,6 +22,7 @@
 
 #include <utility>
 #include <numeric>
+#include <libdevcore/Common.h>
 #include <libsolidity/AST.h>
 #include <libsolidity/ExpressionCompiler.h>
 #include <libsolidity/CompilerContext.h>
@@ -50,14 +51,19 @@ bool ExpressionCompiler::visit(Assignment& _assignment)
 	appendTypeConversion(*_assignment.getRightHandSide().getType(), *_assignment.getType());
 	m_currentLValue.reset();
 	_assignment.getLeftHandSide().accept(*this);
+	if (asserts(m_currentLValue.isValid()))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("LValue not retrieved."));
 
 	Token::Value op = _assignment.getAssignmentOperator();
 	if (op != Token::ASSIGN) // compound assignment
+	{
+		if (m_currentLValue.storesReferenceOnStack())
+			m_context << eth::Instruction::SWAP1 << eth::Instruction::DUP2;
+		m_currentLValue.retrieveValue(_assignment, true);
 		appendOrdinaryBinaryOperatorCode(Token::AssignmentToBinaryOp(op), *_assignment.getType());
-	else
-		m_context << eth::Instruction::POP;
+	}
+	m_currentLValue.storeValue(_assignment);
 
-	storeInLValue(_assignment);
 	return false;
 }
 
@@ -76,23 +82,37 @@ void ExpressionCompiler::endVisit(UnaryOperation& _unaryOperation)
 		m_context << eth::Instruction::NOT;
 		break;
 	case Token::DELETE: // delete
-	{
-		// a -> a xor a (= 0).
 		// @todo semantics change for complex types
-		m_context << eth::Instruction::DUP1 << eth::Instruction::XOR;
-		storeInLValue(_unaryOperation);
+		if (asserts(m_currentLValue.isValid()))
+			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("LValue not retrieved."));
+
+		m_context << u256(0);
+		if (m_currentLValue.storesReferenceOnStack())
+			m_context << eth::Instruction::SWAP1;
+		m_currentLValue.storeValue(_unaryOperation);
 		break;
-	}
 	case Token::INC: // ++ (pre- or postfix)
 	case Token::DEC: // -- (pre- or postfix)
+		if (asserts(m_currentLValue.isValid()))
+			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("LValue not retrieved."));
+		m_currentLValue.retrieveValue(_unaryOperation);
 		if (!_unaryOperation.isPrefixOperation())
-			m_context << eth::Instruction::DUP1;
+		{
+			if (m_currentLValue.storesReferenceOnStack())
+				m_context << eth::Instruction::SWAP1 << eth::Instruction::DUP2;
+			else
+				m_context << eth::Instruction::DUP1;
+		}
 		m_context << u256(1);
 		if (_unaryOperation.getOperator() == Token::INC)
 			m_context << eth::Instruction::ADD;
 		else
 			m_context << eth::Instruction::SWAP1 << eth::Instruction::SUB; // @todo avoid the swap
-		storeInLValue(_unaryOperation, !_unaryOperation.isPrefixOperation());
+		// Stack for prefix: [ref] (*ref)+-1
+		// Stack for postfix: *ref [ref] (*ref)+-1
+		if (m_currentLValue.storesReferenceOnStack())
+			m_context << eth::Instruction::SWAP1;
+		m_currentLValue.storeValue(_unaryOperation, !_unaryOperation.isPrefixOperation());
 		break;
 	case Token::ADD: // +
 		// unary add, so basically no-op
@@ -151,12 +171,6 @@ bool ExpressionCompiler::visit(FunctionCall& _functionCall)
 	{
 		// Calling convention: Caller pushes return address and arguments
 		// Callee removes them and pushes return values
-		m_currentLValue.reset();
-		_functionCall.getExpression().accept(*this);
-		if (asserts(m_currentLValue.isInCode()))
-			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Code reference expected."));
-		eth::AssemblyItem functionTag(eth::PushTag, m_currentLValue.location);
-
 		FunctionDefinition const& function = dynamic_cast<FunctionType const&>(*_functionCall.getExpression().getType()).getFunction();
 
 		eth::AssemblyItem returnLabel = m_context.pushNewTag();
@@ -168,8 +182,12 @@ bool ExpressionCompiler::visit(FunctionCall& _functionCall)
 			arguments[i]->accept(*this);
 			appendTypeConversion(*arguments[i]->getType(), *function.getParameters()[i]->getType());
 		}
+		m_currentLValue.reset();
+		_functionCall.getExpression().accept(*this);
+		if (asserts(m_currentLValue.isInCode()))
+			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Code reference expected."));
 
-		m_context.appendJumpTo(functionTag);
+		m_context.appendJump();
 		m_context << returnLabel;
 
 		// callee adds return parameters, but removes arguments and return label
@@ -185,30 +203,33 @@ bool ExpressionCompiler::visit(FunctionCall& _functionCall)
 
 void ExpressionCompiler::endVisit(MemberAccess&)
 {
-
+	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Member access not yet implemented."));
 }
 
-void ExpressionCompiler::endVisit(IndexAccess&)
+bool ExpressionCompiler::visit(IndexAccess& _indexAccess)
 {
+	m_currentLValue.reset();
+	_indexAccess.getBaseExpression().accept(*this);
+	if (asserts(m_currentLValue.isInStorage()))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Index access to a non-storage value."));
+	_indexAccess.getIndexExpression().accept(*this);
+	appendTypeConversion(*_indexAccess.getIndexExpression().getType(),
+						 *dynamic_cast<MappingType const&>(*_indexAccess.getBaseExpression().getType()).getKeyType(),
+						 true);
+	// @todo move this once we actually use memory
+	m_context << u256(32) << eth::Instruction::MSTORE << u256(0) << eth::Instruction::MSTORE;
+	m_context << u256(64) << u256(0) << eth::Instruction::SHA3;
+
+	m_currentLValue = LValue(m_context, LValue::STORAGE);
+	m_currentLValue.retrieveValueIfLValueNotRequested(_indexAccess);
 
+	return false;
 }
 
 void ExpressionCompiler::endVisit(Identifier& _identifier)
 {
-	Declaration const* declaration = _identifier.getReferencedDeclaration();
-	if (m_context.isLocalVariable(declaration))
-		m_currentLValue = LValueLocation(LValueLocation::STACK,
-										 m_context.getBaseStackOffsetOfVariable(*declaration));
-	else if (m_context.isStateVariable(declaration))
-		m_currentLValue = LValueLocation(LValueLocation::STORAGE,
-										 m_context.getStorageLocationOfVariable(*declaration));
-	else if (m_context.isFunctionDefinition(declaration))
-		m_currentLValue = LValueLocation(LValueLocation::CODE,
-										 m_context.getFunctionEntryLabel(dynamic_cast<FunctionDefinition const&>(*declaration)).data());
-	else
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Identifier type not supported or identifier not found."));
-
-	retrieveLValueValue(_identifier);
+	m_currentLValue.fromDeclaration(_identifier, *_identifier.getReferencedDeclaration());
+	m_currentLValue.retrieveValueIfLValueNotRequested(_identifier);
 }
 
 void ExpressionCompiler::endVisit(Literal& _literal)
@@ -371,66 +392,104 @@ void ExpressionCompiler::appendHighBitsCleanup(IntegerType const& _typeOnStack)
 		m_context << ((u256(1) << _typeOnStack.getNumBits()) - 1) << eth::Instruction::AND;
 }
 
-void ExpressionCompiler::retrieveLValueValue(Expression const& _expression)
+void ExpressionCompiler::LValue::retrieveValue(Expression const& _expression, bool _remove) const
 {
-	switch (m_currentLValue.locationType)
+	switch (m_type)
 	{
-	case LValueLocation::CODE:
-		// not stored on the stack
+	case CODE:
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Tried to retrieve value of a function."));
 		break;
-	case LValueLocation::STACK:
+	case STACK:
 	{
-		unsigned stackPos = m_context.baseToCurrentStackOffset(unsigned(m_currentLValue.location));
+		unsigned stackPos = m_context->baseToCurrentStackOffset(unsigned(m_baseStackOffset));
 		if (stackPos >= 15) //@todo correct this by fetching earlier or moving to memory
 			BOOST_THROW_EXCEPTION(CompilerError() << errinfo_sourceLocation(_expression.getLocation())
 												  << errinfo_comment("Stack too deep."));
-		m_context << eth::dupInstruction(stackPos + 1);
+		*m_context << eth::dupInstruction(stackPos + 1);
 		break;
 	}
-	case LValueLocation::STORAGE:
-		m_context << m_currentLValue.location << eth::Instruction::SLOAD;
+	case STORAGE:
+		if (!_remove)
+			*m_context << eth::Instruction::DUP1;
+		*m_context << eth::Instruction::SLOAD;
 		break;
-	case LValueLocation::MEMORY:
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Location type not yet implemented."));
+	case MEMORY:
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_sourceLocation(_expression.getLocation())
+													  << errinfo_comment("Location type not yet implemented."));
 		break;
 	default:
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unsupported location type."));
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_sourceLocation(_expression.getLocation())
+													  << errinfo_comment("Unsupported location type."));
 		break;
 	}
 }
 
-void ExpressionCompiler::storeInLValue(Expression const& _expression, bool _move)
+void ExpressionCompiler::LValue::storeValue(Expression const& _expression, bool _move) const
 {
-	switch (m_currentLValue.locationType)
+	switch (m_type)
 	{
-	case LValueLocation::STACK:
+	case STACK:
 	{
-		unsigned stackPos = m_context.baseToCurrentStackOffset(unsigned(m_currentLValue.location));
+		unsigned stackPos = m_context->baseToCurrentStackOffset(unsigned(m_baseStackOffset));
 		if (stackPos > 16)
 			BOOST_THROW_EXCEPTION(CompilerError() << errinfo_sourceLocation(_expression.getLocation())
 												  << errinfo_comment("Stack too deep."));
 		else if (stackPos > 0)
-			m_context << eth::swapInstruction(stackPos) << eth::Instruction::POP;
+			*m_context << eth::swapInstruction(stackPos) << eth::Instruction::POP;
 		if (!_move)
-			retrieveLValueValue(_expression);
+			retrieveValue(_expression);
 		break;
 	}
-	case LValueLocation::STORAGE:
+	case LValue::STORAGE:
 		if (!_move)
-			m_context << eth::Instruction::DUP1;
-		m_context << m_currentLValue.location << eth::Instruction::SSTORE;
+			*m_context << eth::Instruction::DUP2 << eth::Instruction::SWAP1;
+		*m_context << eth::Instruction::SSTORE;
 		break;
-	case LValueLocation::CODE:
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Location type does not support assignment."));
+	case LValue::CODE:
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_sourceLocation(_expression.getLocation())
+													  << errinfo_comment("Location type does not support assignment."));
 		break;
-	case LValueLocation::MEMORY:
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Location type not yet implemented."));
+	case LValue::MEMORY:
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_sourceLocation(_expression.getLocation())
+													  << errinfo_comment("Location type not yet implemented."));
 		break;
 	default:
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unsupported location type."));
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_sourceLocation(_expression.getLocation())
+													  << errinfo_comment("Unsupported location type."));
 		break;
 	}
 }
 
+void ExpressionCompiler::LValue::retrieveValueIfLValueNotRequested(const Expression& _expression)
+{
+	if (!_expression.lvalueRequested())
+	{
+		retrieveValue(_expression, true);
+		reset();
+	}
+}
+
+void ExpressionCompiler::LValue::fromDeclaration( Expression const& _expression, Declaration const& _declaration)
+{
+	if (m_context->isLocalVariable(&_declaration))
+	{
+		m_type = STACK;
+		m_baseStackOffset = m_context->getBaseStackOffsetOfVariable(_declaration);
+	}
+	else if (m_context->isStateVariable(&_declaration))
+	{
+		m_type = STORAGE;
+		*m_context << m_context->getStorageLocationOfVariable(_declaration);
+	}
+	else if (m_context->isFunctionDefinition(&_declaration))
+	{
+		m_type = CODE;
+		*m_context << m_context->getFunctionEntryLabel(dynamic_cast<FunctionDefinition const&>(_declaration)).pushTag();
+	}
+	else
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_sourceLocation(_expression.getLocation())
+													  << errinfo_comment("Identifier type not supported or identifier not found."));
+}
+
 }
 }
diff --git a/libsolidity/ExpressionCompiler.h b/libsolidity/ExpressionCompiler.h
index bd5a9f866..f52da29ec 100644
--- a/libsolidity/ExpressionCompiler.h
+++ b/libsolidity/ExpressionCompiler.h
@@ -20,6 +20,7 @@
  * Solidity AST to EVM bytecode compiler for expressions.
  */
 
+#include <boost/noncopyable.hpp>
 #include <libdevcore/Common.h>
 #include <libsolidity/ASTVisitor.h>
 
@@ -49,14 +50,15 @@ public:
 	static void appendTypeConversion(CompilerContext& _context, Type const& _typeOnStack, Type const& _targetType);
 
 private:
-	ExpressionCompiler(CompilerContext& _compilerContext): m_context(_compilerContext) {}
+	ExpressionCompiler(CompilerContext& _compilerContext):
+		m_context(_compilerContext), m_currentLValue(m_context) {}
 
 	virtual bool visit(Assignment& _assignment) override;
 	virtual void endVisit(UnaryOperation& _unaryOperation) override;
 	virtual bool visit(BinaryOperation& _binaryOperation) override;
 	virtual bool visit(FunctionCall& _functionCall) override;
 	virtual void endVisit(MemberAccess& _memberAccess) override;
-	virtual void endVisit(IndexAccess& _indexAccess) override;
+	virtual bool visit(IndexAccess& _indexAccess) override;
 	virtual void endVisit(Identifier& _identifier) override;
 	virtual void endVisit(Literal& _literal) override;
 
@@ -79,37 +81,58 @@ private:
 	//// Appends code that cleans higher-order bits for integer types.
 	void appendHighBitsCleanup(IntegerType const& _typeOnStack);
 
-	/// Copies the value of the current lvalue to the top of the stack.
-	void retrieveLValueValue(Expression const& _expression);
-	/// Stores the value on top of the stack in the current lvalue. Removes it from the stack if
-	/// @a _move is true.
-	void storeInLValue(Expression const& _expression, bool _move = false);
-
 	/**
-	 * Location of an lvalue, either in code (for a function) on the stack, in the storage or memory.
+	 * Helper class to store and retrieve lvalues to and from various locations.
+	 * All types except STACK store a reference in a slot on the stack, STACK just stores the
+	 * base stack offset of the variable in @a m_baseStackOffset.
 	 */
-	struct LValueLocation
+	class LValue
 	{
-		enum LocationType { INVALID, CODE, STACK, MEMORY, STORAGE };
-
-		LValueLocation() { reset(); }
-		LValueLocation(LocationType _type, u256 const& _location): locationType(_type), location(_location) {}
-		void reset() { locationType = INVALID; location = 0; }
-		bool isValid() const { return locationType != INVALID; }
-		bool isInCode() const { return locationType == CODE; }
-		bool isInOnStack() const { return locationType == STACK; }
-		bool isInMemory() const { return locationType == MEMORY; }
-		bool isInStorage() const { return locationType == STORAGE; }
-
-		LocationType locationType;
-		/// Depending on the type, this is the id of a tag (code), the base offset of a stack
-		/// variable (@see CompilerContext::getBaseStackOffsetOfVariable) or the offset in
-		/// storage or memory.
-		u256 location;
+	public:
+		enum LValueType { NONE, CODE, STACK, MEMORY, STORAGE };
+
+		explicit LValue(CompilerContext& _compilerContext): m_context(&_compilerContext) { reset(); }
+		LValue(CompilerContext& _compilerContext, LValueType _type, unsigned _baseStackOffset = 0):
+			m_context(&_compilerContext), m_type(_type), m_baseStackOffset(_baseStackOffset) {}
+
+		/// Set type according to the declaration and retrieve the reference.
+		/// @a _expression is the current expression, used for error reporting.
+		void fromDeclaration(Expression const& _expression, Declaration const& _declaration);
+		void reset() { m_type = NONE; m_baseStackOffset = 0; }
+
+		bool isValid() const { return m_type != NONE; }
+		bool isInCode() const { return m_type == CODE; }
+		bool isInOnStack() const { return m_type == STACK; }
+		bool isInMemory() const { return m_type == MEMORY; }
+		bool isInStorage() const { return m_type == STORAGE; }
+
+		/// @returns true if this lvalue reference type occupies a slot on the stack.
+		bool storesReferenceOnStack() const { return m_type == STORAGE || m_type == MEMORY || m_type == CODE; }
+
+		/// Copies the value of the current lvalue to the top of the stack and, if @a _remove is true,
+		/// also removes the reference from the stack (note that is does not reset the type to @a NONE).
+		/// @a _expression is the current expression, used for error reporting.
+		void retrieveValue(Expression const& _expression, bool _remove = false) const;
+		/// Stores a value (from the stack directly beneath the reference, which is assumed to
+		/// be on the top of the stack, if any) in the lvalue and removes the reference.
+		/// Also removes the stored value from the stack if @a _move is
+		/// true. @a _expression is the current expression, used for error reporting.
+		void storeValue(Expression const& _expression, bool _move = false) const;
+
+		/// Convenience function to convert the stored reference to a value and reset type to NONE if
+		/// the reference was not requested by @a _expression.
+		void retrieveValueIfLValueNotRequested(Expression const& _expression);
+
+	private:
+		CompilerContext* m_context;
+		LValueType m_type;
+		/// If m_type is STACK, this is base stack offset (@see
+		/// CompilerContext::getBaseStackOffsetOfVariable) of a local variable.
+		unsigned m_baseStackOffset;
 	};
 
-	LValueLocation m_currentLValue;
 	CompilerContext& m_context;
+	LValue m_currentLValue;
 };
 
 
diff --git a/libsolidity/NameAndTypeResolver.cpp b/libsolidity/NameAndTypeResolver.cpp
index 0578e5996..4a15fe794 100644
--- a/libsolidity/NameAndTypeResolver.cpp
+++ b/libsolidity/NameAndTypeResolver.cpp
@@ -52,7 +52,7 @@ void NameAndTypeResolver::resolveNamesAndTypes(ContractDefinition& _contract)
 	for (ASTPointer<FunctionDefinition> const& function: _contract.getDefinedFunctions())
 	{
 		m_currentScope = &m_scopes[function.get()];
-		function->getBody().checkTypeRequirements();
+		function->checkTypeRequirements();
 	}
 	m_currentScope = &m_scopes[nullptr];
 }
@@ -186,9 +186,8 @@ bool ReferencesResolver::visit(Return& _return)
 	return true;
 }
 
-bool ReferencesResolver::visit(Mapping&)
+bool ReferencesResolver::visit(Mapping& _mapping)
 {
-	// @todo
 	return true;
 }
 
diff --git a/libsolidity/Types.cpp b/libsolidity/Types.cpp
index 3a4112c45..e37ed3e5b 100644
--- a/libsolidity/Types.cpp
+++ b/libsolidity/Types.cpp
@@ -63,9 +63,11 @@ shared_ptr<Type> Type::fromUserDefinedTypeName(UserDefinedTypeName const& _typeN
 	return make_shared<StructType>(*_typeName.getReferencedStruct());
 }
 
-shared_ptr<Type> Type::fromMapping(Mapping const&)
+shared_ptr<Type> Type::fromMapping(Mapping const& _typeName)
 {
-	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Mapping types not yet implemented."));
+	shared_ptr<Type const> keyType = _typeName.getKeyType().toType();
+	shared_ptr<Type const> valueType = _typeName.getValueType().toType();
+	return make_shared<MappingType>(keyType, valueType);
 }
 
 shared_ptr<Type> Type::forLiteral(Literal const& _literal)
diff --git a/libsolidity/Types.h b/libsolidity/Types.h
index 607ee3a6f..b9bb74dbb 100644
--- a/libsolidity/Types.h
+++ b/libsolidity/Types.h
@@ -35,7 +35,7 @@ namespace dev
 namespace solidity
 {
 
-// @todo realMxN, string<N>, mapping
+// @todo realMxN, string<N>
 
 /**
  * Abstract base class that forms the root of the type hierarchy.
@@ -78,6 +78,8 @@ public:
 	/// @returns number of bytes required to hold this value in storage.
 	/// For dynamically "allocated" types, it returns the size of the statically allocated head,
 	virtual u256 getStorageSize() const { return 1; }
+	/// Returns false if the type cannot live outside the storage, i.e. if it includes some mapping.
+	virtual bool canLiveOutsideStorage() const { return true; }
 
 	virtual std::string toString() const = 0;
 	virtual u256 literalValue(Literal const&) const
@@ -182,6 +184,8 @@ public:
 
 	virtual bool operator==(Type const& _other) const override;
 	virtual u256 getStorageSize() const;
+	//@todo it can, if its members can
+	virtual bool canLiveOutsideStorage() const { return false; }
 	virtual std::string toString() const override { return "struct{...}"; }
 
 private:
@@ -202,6 +206,7 @@ public:
 	virtual bool operator==(Type const& _other) const override;
 	virtual std::string toString() const override { return "function(...)returns(...)"; }
 	virtual u256 getStorageSize() const { BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Storage size of non-storable function type requested.")); }
+	virtual bool canLiveOutsideStorage() const { return false; }
 
 private:
 	FunctionDefinition const& m_function;
@@ -214,11 +219,15 @@ class MappingType: public Type
 {
 public:
 	virtual Category getCategory() const override { return Category::MAPPING; }
-	MappingType() {}
+	MappingType(std::shared_ptr<Type const> _keyType, std::shared_ptr<Type const> _valueType):
+		m_keyType(_keyType), m_valueType(_valueType) {}
 
 	virtual bool operator==(Type const& _other) const override;
 	virtual std::string toString() const override { return "mapping(...=>...)"; }
+	virtual bool canLiveOutsideStorage() const { return false; }
 
+	std::shared_ptr<Type const> getKeyType() const { return m_keyType; }
+	std::shared_ptr<Type const> getValueType() const { return m_valueType; }
 private:
 	std::shared_ptr<Type const> m_keyType;
 	std::shared_ptr<Type const> m_valueType;
@@ -236,6 +245,7 @@ public:
 
 	virtual std::string toString() const override { return "void"; }
 	virtual u256 getStorageSize() const { BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Storage size of non-storable void type requested.")); }
+	virtual bool canLiveOutsideStorage() const { return false; }
 };
 
 /**
@@ -252,6 +262,7 @@ public:
 
 	virtual bool operator==(Type const& _other) const override;
 	virtual u256 getStorageSize() const { BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Storage size of non-storable type type requested.")); }
+	virtual bool canLiveOutsideStorage() const { return false; }
 	virtual std::string toString() const override { return "type(" + m_actualType->toString() + ")"; }
 
 private:
diff --git a/test/solidityCompiler.cpp b/test/solidityCompiler.cpp
index 054ad3297..e0635b6ae 100644
--- a/test/solidityCompiler.cpp
+++ b/test/solidityCompiler.cpp
@@ -128,8 +128,6 @@ BOOST_AUTO_TEST_CASE(different_argument_numbers)
 					   byte(Instruction::JUMP),
 					   byte(Instruction::JUMPDEST),
 					   // stack here: ret e h f(1,2,3)
-					   byte(Instruction::DUP2),
-					   byte(Instruction::POP),
 					   byte(Instruction::SWAP1),
 					   // stack here: ret e f(1,2,3) h
 					   byte(Instruction::POP),
diff --git a/test/solidityEndToEndTest.cpp b/test/solidityEndToEndTest.cpp
index d905646cb..5e6631df6 100644
--- a/test/solidityEndToEndTest.cpp
+++ b/test/solidityEndToEndTest.cpp
@@ -32,6 +32,9 @@ using namespace std;
 
 namespace dev
 {
+/// Provider another overload for toBigEndian to encode arguments and return values.
+inline bytes toBigEndian(bool _value) { return bytes({byte(_value)}); }
+
 namespace solidity
 {
 namespace test
@@ -137,6 +140,7 @@ private:
 		m_output = executive.out().toVector();
 	}
 
+protected:
 	Address m_contractAddress;
 	eth::State m_state;
 	u256 const m_gasPrice = 100 * eth::szabo;
@@ -496,6 +500,169 @@ BOOST_AUTO_TEST_CASE(state_smoke_test)
 	BOOST_CHECK(callContractFunction(0, bytes(1, 0x00)) == toBigEndian(u256(0x3)));
 }
 
+BOOST_AUTO_TEST_CASE(simple_mapping)
+{
+	char const* sourceCode = "contract test {\n"
+							 "  mapping(uint8 => uint8) table;\n"
+							 "  function get(uint8 k) returns (uint8 v) {\n"
+							 "    return table[k];\n"
+							 "  }\n"
+							 "  function set(uint8 k, uint8 v) {\n"
+							 "    table[k] = v;\n"
+							 "  }\n"
+							 "}";
+	compileAndRun(sourceCode);
+
+	BOOST_CHECK(callContractFunction(0, bytes({0x00})) == bytes({0x00}));
+	BOOST_CHECK(callContractFunction(0, bytes({0x01})) == bytes({0x00}));
+	BOOST_CHECK(callContractFunction(0, bytes({0xa7})) == bytes({0x00}));
+	callContractFunction(1, bytes({0x01, 0xa1}));
+	BOOST_CHECK(callContractFunction(0, bytes({0x00})) == bytes({0x00}));
+	BOOST_CHECK(callContractFunction(0, bytes({0x01})) == bytes({0xa1}));
+	BOOST_CHECK(callContractFunction(0, bytes({0xa7})) == bytes({0x00}));
+	callContractFunction(1, bytes({0x00, 0xef}));
+	BOOST_CHECK(callContractFunction(0, bytes({0x00})) == bytes({0xef}));
+	BOOST_CHECK(callContractFunction(0, bytes({0x01})) == bytes({0xa1}));
+	BOOST_CHECK(callContractFunction(0, bytes({0xa7})) == bytes({0x00}));
+	callContractFunction(1, bytes({0x01, 0x05}));
+	BOOST_CHECK(callContractFunction(0, bytes({0x00})) == bytes({0xef}));
+	BOOST_CHECK(callContractFunction(0, bytes({0x01})) == bytes({0x05}));
+	BOOST_CHECK(callContractFunction(0, bytes({0xa7})) == bytes({0x00}));
+}
+
+BOOST_AUTO_TEST_CASE(mapping_state)
+{
+	char const* sourceCode = "contract Ballot {\n"
+							 "  mapping(address => bool) canVote;\n"
+							 "  mapping(address => uint) voteCount;\n"
+							 "  mapping(address => bool) voted;\n"
+							 "  function getVoteCount(address addr) returns (uint retVoteCount) {\n"
+							 "    return voteCount[addr];\n"
+							 "  }\n"
+							 "  function grantVoteRight(address addr) {\n"
+							 "    canVote[addr] = true;\n"
+							 "  }\n"
+							 "  function vote(address voter, address vote) returns (bool success) {\n"
+							 "    if (!canVote[voter] || voted[voter]) return false;\n"
+							 "    voted[voter] = true;\n"
+							 "    voteCount[vote] = voteCount[vote] + 1;\n"
+							 "    return true;\n"
+							 "  }\n"
+							 "}\n";
+	compileAndRun(sourceCode);
+	class Ballot
+	{
+	public:
+		u256 getVoteCount(u160 _address) { return m_voteCount[_address]; }
+		void grantVoteRight(u160 _address) { m_canVote[_address] = true; }
+		bool vote(u160 _voter, u160 _vote)
+		{
+			if (!m_canVote[_voter] || m_voted[_voter]) return false;
+			m_voted[_voter] = true;
+			m_voteCount[_vote]++;
+			return true;
+		}
+	private:
+		map<u160, bool> m_canVote;
+		map<u160, u256> m_voteCount;
+		map<u160, bool> m_voted;
+	} ballot;
+
+	auto getVoteCount = bind(&Ballot::getVoteCount, &ballot, _1);
+	auto grantVoteRight = bind(&Ballot::grantVoteRight, &ballot, _1);
+	auto vote = bind(&Ballot::vote, &ballot, _1, _2);
+	testSolidityAgainstCpp(0, getVoteCount, u160(0));
+	testSolidityAgainstCpp(0, getVoteCount, u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(2));
+	// voting without vote right shourd be rejected
+	testSolidityAgainstCpp(2, vote, u160(0), u160(2));
+	testSolidityAgainstCpp(0, getVoteCount, u160(0));
+	testSolidityAgainstCpp(0, getVoteCount, u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(2));
+	// grant vote rights
+	testSolidityAgainstCpp(1, grantVoteRight, u160(0));
+	testSolidityAgainstCpp(1, grantVoteRight, u160(1));
+	// vote, should increase 2's vote count
+	testSolidityAgainstCpp(2, vote, u160(0), u160(2));
+	testSolidityAgainstCpp(0, getVoteCount, u160(0));
+	testSolidityAgainstCpp(0, getVoteCount, u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(2));
+	// vote again, should be rejected
+	testSolidityAgainstCpp(2, vote, u160(0), u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(0));
+	testSolidityAgainstCpp(0, getVoteCount, u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(2));
+	// vote without right to vote
+	testSolidityAgainstCpp(2, vote, u160(2), u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(0));
+	testSolidityAgainstCpp(0, getVoteCount, u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(2));
+	// grant vote right and now vote again
+	testSolidityAgainstCpp(1, grantVoteRight, u160(2));
+	testSolidityAgainstCpp(2, vote, u160(2), u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(0));
+	testSolidityAgainstCpp(0, getVoteCount, u160(1));
+	testSolidityAgainstCpp(0, getVoteCount, u160(2));
+}
+
+BOOST_AUTO_TEST_CASE(mapping_state_inc_dec)
+{
+	char const* sourceCode = "contract test {\n"
+							 "  uint value;\n"
+							 "  mapping(uint => uint) table;\n"
+							 "  function f(uint x) returns (uint y) {\n"
+							 "    value = x;\n"
+							 "    if (x > 0) table[++value] = 8;\n"
+							 "    if (x > 1) value--;\n"
+							 "    if (x > 2) table[value]++;\n"
+							 "    return --table[value++];\n"
+							 "  }\n"
+							 "}\n";
+	compileAndRun(sourceCode);
+
+	u256 value = 0;
+	map<u256, u256> table;
+	auto f = [&](u256 const& _x) -> u256
+	{
+		value = _x;
+		if (_x > 0)
+			table[++value] = 8;
+		if (_x > 1)
+			value --;
+		if (_x > 2)
+			table[value]++;
+		return --table[value++];
+	};
+	testSolidityAgainstCppOnRange(0, f, 0, 5);
+}
+
+BOOST_AUTO_TEST_CASE(multi_level_mapping)
+{
+	char const* sourceCode = "contract test {\n"
+							 "  mapping(uint => mapping(uint => uint)) table;\n"
+							 "  function f(uint x, uint y, uint z) returns (uint w) {\n"
+							 "    if (z == 0) return table[x][y];\n"
+							 "    else return table[x][y] = z;\n"
+							 "  }\n"
+							 "}\n";
+	compileAndRun(sourceCode);
+
+	map<u256, map<u256, u256>> table;
+	auto f = [&](u256 const& _x, u256 const& _y, u256 const& _z) -> u256
+	{
+		if (_z == 0) return table[_x][_y];
+		else return table[_x][_y] = _z;
+	};
+	testSolidityAgainstCpp(0, f, u256(4), u256(5), u256(0));
+	testSolidityAgainstCpp(0, f, u256(5), u256(4), u256(0));
+	testSolidityAgainstCpp(0, f, u256(4), u256(5), u256(9));
+	testSolidityAgainstCpp(0, f, u256(4), u256(5), u256(0));
+	testSolidityAgainstCpp(0, f, u256(5), u256(4), u256(0));
+	testSolidityAgainstCpp(0, f, u256(5), u256(4), u256(7));
+	testSolidityAgainstCpp(0, f, u256(4), u256(5), u256(0));
+	testSolidityAgainstCpp(0, f, u256(5), u256(4), u256(0));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }