diff --git a/libsolidity/AST.cpp b/libsolidity/AST.cpp
index 0ecb639f0..f9c49adc5 100644
--- a/libsolidity/AST.cpp
+++ b/libsolidity/AST.cpp
@@ -293,9 +293,10 @@ void Break::checkTypeRequirements()
 
 void Return::checkTypeRequirements()
 {
-	assert(m_returnParameters);
 	if (!m_expression)
 		return;
+	if (asserts(m_returnParameters))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Return parameters not assigned."));
 	if (m_returnParameters->getParameters().size() != 1)
 		BOOST_THROW_EXCEPTION(createTypeError("Different number of arguments in return statement "
 											  "than in returns declaration."));
@@ -377,7 +378,6 @@ void BinaryOperation::checkTypeRequirements()
 		m_type = make_shared<BoolType>();
 	else
 	{
-		assert(Token::isBinaryOp(m_operator));
 		m_type = m_commonType;
 		if (!m_commonType->acceptsBinaryOperator(m_operator))
 			BOOST_THROW_EXCEPTION(createTypeError("Operator not compatible with type."));
@@ -393,25 +393,22 @@ void FunctionCall::checkTypeRequirements()
 	Type const* expressionType = m_expression->getType().get();
 	if (isTypeConversion())
 	{
-		TypeType const* type = dynamic_cast<TypeType const*>(expressionType);
-		assert(type);
+		TypeType const& type = dynamic_cast<TypeType const&>(*expressionType);
 		//@todo for structs, we have to check the number of arguments to be equal to the
 		// number of non-mapping members
 		if (m_arguments.size() != 1)
 			BOOST_THROW_EXCEPTION(createTypeError("More than one argument for "
 														   "explicit type conersion."));
-		if (!m_arguments.front()->getType()->isExplicitlyConvertibleTo(*type->getActualType()))
+		if (!m_arguments.front()->getType()->isExplicitlyConvertibleTo(*type.getActualType()))
 			BOOST_THROW_EXCEPTION(createTypeError("Explicit type conversion not allowed."));
-		m_type = type->getActualType();
+		m_type = type.getActualType();
 	}
 	else
 	{
 		//@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
-		FunctionType const* function = dynamic_cast<FunctionType const*>(expressionType);
-		assert(function);
-		FunctionDefinition const& fun = function->getFunction();
+		FunctionDefinition const& fun = dynamic_cast<FunctionType const&>(*expressionType).getFunction();
 		vector<ASTPointer<VariableDeclaration>> const& parameters = fun.getParameters();
 		if (parameters.size() != m_arguments.size())
 			BOOST_THROW_EXCEPTION(createTypeError("Wrong argument count for function call."));
@@ -434,19 +431,21 @@ bool FunctionCall::isTypeConversion() const
 
 void MemberAccess::checkTypeRequirements()
 {
-	assert(false); // not yet implemented
+	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Member access not yet implemented."));
 	// m_type = ;
 }
 
 void IndexAccess::checkTypeRequirements()
 {
-	assert(false); // not yet implemented
+	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Index access not yet implemented."));
 	// m_type = ;
 }
 
 void Identifier::checkTypeRequirements()
 {
-	assert(m_referencedDeclaration);
+	if (asserts(m_referencedDeclaration))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Identifier not resolved."));
+
 	//@todo these dynamic casts here are not really nice...
 	// is i useful to have an AST visitor here?
 	// or can this already be done in NameAndTypeResolver?
@@ -487,7 +486,7 @@ void Identifier::checkTypeRequirements()
 		m_type = make_shared<TypeType>(make_shared<ContractType>(*contractDef));
 		return;
 	}
-	assert(false); // declaration reference of unknown/forbidden type
+	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Declaration reference of unknown/forbidden type."));
 }
 
 void ElementaryTypeNameExpression::checkTypeRequirements()
diff --git a/libsolidity/AST.h b/libsolidity/AST.h
index 43aa9bf5e..f42ff47d0 100644
--- a/libsolidity/AST.h
+++ b/libsolidity/AST.h
@@ -243,7 +243,10 @@ class ElementaryTypeName: public TypeName
 {
 public:
 	explicit ElementaryTypeName(Location const& _location, Token::Value _type):
-		TypeName(_location), m_type(_type) {}
+		TypeName(_location), m_type(_type)
+	{
+		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); }
 
@@ -407,7 +410,12 @@ public:
 	virtual void checkTypeRequirements() override;
 
 	void setFunctionReturnParameters(ParameterList& _parameters) { m_returnParameters = &_parameters; }
-	ParameterList const& getFunctionReturnParameters() const { assert(m_returnParameters); return *m_returnParameters; }
+	ParameterList const& getFunctionReturnParameters() const
+	{
+		if (asserts(m_returnParameters))
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
+		return *m_returnParameters;
+	}
 	Expression* getExpression() const { return m_expression.get(); }
 
 private:
@@ -495,7 +503,10 @@ public:
 	Assignment(Location const& _location, ASTPointer<Expression> const& _leftHandSide,
 			   Token::Value _assignmentOperator, ASTPointer<Expression> const& _rightHandSide):
 		Expression(_location), m_leftHandSide(_leftHandSide),
-		m_assigmentOperator(_assignmentOperator), m_rightHandSide(_rightHandSide) {}
+		m_assigmentOperator(_assignmentOperator), m_rightHandSide(_rightHandSide)
+	{
+		if (asserts(Token::isAssignmentOp(_assignmentOperator))) BOOST_THROW_EXCEPTION(InternalCompilerError());
+	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void checkTypeRequirements() override;
 
@@ -519,7 +530,10 @@ public:
 	UnaryOperation(Location const& _location, Token::Value _operator,
 				   ASTPointer<Expression> const& _subExpression, bool _isPrefix):
 		Expression(_location), m_operator(_operator),
-		m_subExpression(_subExpression), m_isPrefix(_isPrefix) {}
+		m_subExpression(_subExpression), m_isPrefix(_isPrefix)
+	{
+		if (asserts(Token::isUnaryOp(_operator))) BOOST_THROW_EXCEPTION(InternalCompilerError());
+	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void checkTypeRequirements() override;
 
@@ -541,7 +555,10 @@ class BinaryOperation: public Expression
 public:
 	BinaryOperation(Location const& _location, ASTPointer<Expression> const& _left,
 					Token::Value _operator, ASTPointer<Expression> const& _right):
-		Expression(_location), m_left(_left), m_operator(_operator), m_right(_right) {}
+		Expression(_location), m_left(_left), m_operator(_operator), m_right(_right)
+	{
+		if (asserts(Token::isBinaryOp(_operator) || Token::isCompareOp(_operator))) BOOST_THROW_EXCEPTION(InternalCompilerError());
+	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void checkTypeRequirements() override;
 
@@ -658,7 +675,10 @@ class ElementaryTypeNameExpression: public PrimaryExpression
 {
 public:
 	ElementaryTypeNameExpression(Location const& _location, Token::Value _typeToken):
-		PrimaryExpression(_location), m_typeToken(_typeToken) {}
+		PrimaryExpression(_location), m_typeToken(_typeToken)
+	{
+		if (asserts(Token::isElementaryTypeName(_typeToken))) BOOST_THROW_EXCEPTION(InternalCompilerError());
+	}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void checkTypeRequirements() override;
 
diff --git a/libsolidity/Compiler.cpp b/libsolidity/Compiler.cpp
index a44c177d7..654eceadb 100644
--- a/libsolidity/Compiler.cpp
+++ b/libsolidity/Compiler.cpp
@@ -252,14 +252,16 @@ bool Compiler::visit(WhileStatement& _whileStatement)
 
 bool Compiler::visit(Continue&)
 {
-	assert(!m_continueTags.empty());
+	if (asserts(!m_continueTags.empty()))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Jump tag not available for \"continue\"."));
 	m_context.appendJumpTo(m_continueTags.back());
 	return false;
 }
 
 bool Compiler::visit(Break&)
 {
-	assert(!m_breakTags.empty());
+	if (asserts(!m_breakTags.empty()))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Jump tag not available for \"break\"."));
 	m_context.appendJumpTo(m_breakTags.back());
 	return false;
 }
diff --git a/libsolidity/CompilerContext.cpp b/libsolidity/CompilerContext.cpp
index b8f57618b..44d0844c2 100644
--- a/libsolidity/CompilerContext.cpp
+++ b/libsolidity/CompilerContext.cpp
@@ -20,7 +20,6 @@
  * Utilities for the solidity compiler.
  */
 
-#include <cassert>
 #include <utility>
 #include <numeric>
 #include <libsolidity/AST.h>
@@ -45,14 +44,16 @@ void CompilerContext::initializeLocalVariables(unsigned _numVariables)
 int CompilerContext::getStackPositionOfVariable(const Declaration& _declaration)
 {
 	auto res = find(begin(m_localVariables), end(m_localVariables), &_declaration);
-	assert(res != m_localVariables.end());
+	if (asserts(res != m_localVariables.end()))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Variable not found on stack."));
 	return end(m_localVariables) - res - 1 + m_asm.deposit();
 }
 
 eth::AssemblyItem CompilerContext::getFunctionEntryLabel(const FunctionDefinition& _function) const
 {
 	auto res = m_functionEntryLabels.find(&_function);
-	assert(res != m_functionEntryLabels.end());
+	if (asserts(res != m_functionEntryLabels.end()))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Function entry label not found."));
 	return res->second.tag();
 }
 
diff --git a/libsolidity/Exceptions.h b/libsolidity/Exceptions.h
index 1d981e7c0..1903c1dc2 100644
--- a/libsolidity/Exceptions.h
+++ b/libsolidity/Exceptions.h
@@ -35,6 +35,7 @@ struct ParserError: virtual Exception {};
 struct TypeError: virtual Exception {};
 struct DeclarationError: virtual Exception {};
 struct CompilerError: virtual Exception {};
+struct InternalCompilerError: 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/ExpressionCompiler.cpp b/libsolidity/ExpressionCompiler.cpp
index f9cbee377..d23579b11 100644
--- a/libsolidity/ExpressionCompiler.cpp
+++ b/libsolidity/ExpressionCompiler.cpp
@@ -20,7 +20,6 @@
  * Solidity AST to EVM bytecode compiler for expressions.
  */
 
-#include <cassert>
 #include <utility>
 #include <numeric>
 #include <libsolidity/AST.h>
@@ -105,7 +104,8 @@ void ExpressionCompiler::endVisit(UnaryOperation& _unaryOperation)
 		m_context << u256(0) << eth::Instruction::SUB;
 		break;
 	default:
-		assert(false); // invalid operation
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid unary operator: " +
+																		 string(Token::toString(_unaryOperation.getOperator()))));
 	}
 }
 
@@ -127,7 +127,8 @@ bool ExpressionCompiler::visit(BinaryOperation& _binaryOperation)
 		rightExpression.accept(*this);
 
 		// the types to compare have to be the same, but the resulting type is always bool
-		assert(*leftExpression.getType() == *rightExpression.getType());
+		if (asserts(*leftExpression.getType() == *rightExpression.getType()))
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
 		appendCompareOperatorCode(op, *leftExpression.getType());
 	}
 	else
@@ -148,7 +149,8 @@ bool ExpressionCompiler::visit(FunctionCall& _functionCall)
 	if (_functionCall.isTypeConversion())
 	{
 		//@todo we only have integers and bools for now which cannot be explicitly converted
-		assert(_functionCall.getArguments().size() == 1);
+		if (asserts(_functionCall.getArguments().size() == 1))
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
 		Expression& firstArgument = *_functionCall.getArguments().front();
 		firstArgument.accept(*this);
 		cleanHigherOrderBitsIfNeeded(*firstArgument.getType(), *_functionCall.getType());
@@ -159,28 +161,28 @@ bool ExpressionCompiler::visit(FunctionCall& _functionCall)
 		// Callee removes them and pushes return values
 		m_currentLValue = nullptr;
 		_functionCall.getExpression().accept(*this);
-		FunctionDefinition const* function = dynamic_cast<FunctionDefinition*>(m_currentLValue);
-		assert(function);
+		FunctionDefinition const& function = dynamic_cast<FunctionDefinition&>(*m_currentLValue);
 
 		eth::AssemblyItem returnLabel = m_context.pushNewTag();
 		std::vector<ASTPointer<Expression>> const& arguments = _functionCall.getArguments();
-		assert(arguments.size() == function->getParameters().size());
+		if (asserts(arguments.size() == function.getParameters().size()))
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
 		for (unsigned i = 0; i < arguments.size(); ++i)
 		{
 			arguments[i]->accept(*this);
 			cleanHigherOrderBitsIfNeeded(*arguments[i]->getType(),
-										 *function->getParameters()[i]->getType());
+										 *function.getParameters()[i]->getType());
 		}
 
-		m_context.appendJumpTo(m_context.getFunctionEntryLabel(*function));
+		m_context.appendJumpTo(m_context.getFunctionEntryLabel(function));
 		m_context << returnLabel;
 
 		// callee adds return parameters, but removes arguments and return label
-		m_context.adjustStackOffset(function->getReturnParameters().size() - arguments.size() - 1);
+		m_context.adjustStackOffset(function.getReturnParameters().size() - arguments.size() - 1);
 
 		// @todo for now, the return value of a function is its first return value, so remove
 		// all others
-		for (unsigned i = 1; i < function->getReturnParameters().size(); ++i)
+		for (unsigned i = 1; i < function.getReturnParameters().size(); ++i)
 			m_context << eth::Instruction::POP;
 	}
 	return false;
@@ -227,7 +229,7 @@ void ExpressionCompiler::endVisit(Literal& _literal)
 		m_context << _literal.getType()->literalValue(_literal);
 		break;
 	default:
-		assert(false); // @todo
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Only integer and boolean literals implemented for now."));
 	}
 }
 
@@ -249,15 +251,15 @@ void ExpressionCompiler::cleanHigherOrderBitsIfNeeded(Type const& _typeOnStack,
 	{
 		// If we get here, there is either an implementation missing to clean higher oder bits
 		// for non-integer types that are explicitly convertible or we got here in error.
-		assert(!_typeOnStack.isExplicitlyConvertibleTo(_targetType));
-		assert(false); // these types should not be convertible.
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid type conversion requested."));
 	}
 }
 
 void ExpressionCompiler::appendAndOrOperatorCode(BinaryOperation& _binaryOperation)
 {
 	Token::Value const op = _binaryOperation.getOperator();
-	assert(op == Token::OR || op == Token::AND);
+	if (asserts(op == Token::OR || op == Token::AND))
+		BOOST_THROW_EXCEPTION(InternalCompilerError());
 
 	_binaryOperation.getLeftExpression().accept(*this);
 	m_context << eth::Instruction::DUP1;
@@ -279,9 +281,8 @@ void ExpressionCompiler::appendCompareOperatorCode(Token::Value _operator, Type
 	}
 	else
 	{
-		IntegerType const* type = dynamic_cast<IntegerType const*>(&_type);
-		assert(type);
-		bool const isSigned = type->isSigned();
+		IntegerType const& type = dynamic_cast<IntegerType const&>(_type);
+		bool const isSigned = type.isSigned();
 
 		// note that EVM opcodes compare like "stack[0] < stack[1]",
 		// but our left value is at stack[1], so everyhing is reversed.
@@ -302,7 +303,7 @@ void ExpressionCompiler::appendCompareOperatorCode(Token::Value _operator, Type
 			m_context << (isSigned ? eth::Instruction::SGT : eth::Instruction::GT);
 			break;
 		default:
-			assert(false);
+			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown comparison operator."));
 		}
 	}
 }
@@ -316,14 +317,13 @@ void ExpressionCompiler::appendOrdinaryBinaryOperatorCode(Token::Value _operator
 	else if (Token::isShiftOp(_operator))
 		appendShiftOperatorCode(_operator);
 	else
-		assert(false); // unknown binary operator
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown binary operator."));
 }
 
 void ExpressionCompiler::appendArithmeticOperatorCode(Token::Value _operator, Type const& _type)
 {
-	IntegerType const* type = dynamic_cast<IntegerType const*>(&_type);
-	assert(type);
-	bool const isSigned = type->isSigned();
+	IntegerType const& type = dynamic_cast<IntegerType const&>(_type);
+	bool const isSigned = type.isSigned();
 
 	switch (_operator)
 	{
@@ -343,7 +343,7 @@ void ExpressionCompiler::appendArithmeticOperatorCode(Token::Value _operator, Ty
 		m_context << eth::Instruction::SWAP1 << (isSigned ? eth::Instruction::SMOD : eth::Instruction::MOD);
 		break;
 	default:
-		assert(false);
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown arithmetic operator."));
 	}
 }
 
@@ -361,22 +361,21 @@ void ExpressionCompiler::appendBitOperatorCode(Token::Value _operator)
 		m_context << eth::Instruction::XOR;
 		break;
 	default:
-		assert(false);
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown bit operator."));
 	}
 }
 
 void ExpressionCompiler::appendShiftOperatorCode(Token::Value _operator)
 {
+	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Shift operators not yet implemented."));
 	switch (_operator)
 	{
 	case Token::SHL:
-		assert(false); //@todo
 		break;
 	case Token::SAR:
-		assert(false); //@todo
 		break;
 	default:
-		assert(false);
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown shift operator."));
 	}
 }
 
@@ -402,7 +401,8 @@ void ExpressionCompiler::moveToLValue(Expression const& _expression)
 
 unsigned ExpressionCompiler::stackPositionOfLValue() const
 {
-	assert(m_currentLValue);
+	if (asserts(m_currentLValue))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("LValue not available on request."));
 	return m_context.getStackPositionOfVariable(*m_currentLValue);
 }
 
diff --git a/libsolidity/NameAndTypeResolver.cpp b/libsolidity/NameAndTypeResolver.cpp
index 4b77ed132..0578e5996 100644
--- a/libsolidity/NameAndTypeResolver.cpp
+++ b/libsolidity/NameAndTypeResolver.cpp
@@ -20,7 +20,6 @@
  * Parser part that determines the declarations corresponding to names and the types of expressions.
  */
 
-#include <cassert>
 #include <libsolidity/NameAndTypeResolver.h>
 #include <libsolidity/AST.h>
 #include <libsolidity/Exceptions.h>
@@ -123,7 +122,8 @@ void DeclarationRegistrationHelper::endVisit(VariableDefinition& _variableDefini
 {
 	// Register the local variables with the function
 	// This does not fit here perfectly, but it saves us another AST visit.
-	assert(m_currentFunction);
+	if (asserts(m_currentFunction))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Variable definition without function."));
 	m_currentFunction->addLocalVariable(_variableDefinition.getDeclaration());
 }
 
@@ -138,19 +138,22 @@ void DeclarationRegistrationHelper::enterNewSubScope(ASTNode& _node)
 	map<ASTNode const*, Scope>::iterator iter;
 	bool newlyAdded;
 	tie(iter, newlyAdded) = m_scopes.emplace(&_node, Scope(m_currentScope));
-	assert(newlyAdded);
+	if (asserts(newlyAdded))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unable to add new scope."));
 	m_currentScope = &iter->second;
 }
 
 void DeclarationRegistrationHelper::closeCurrentScope()
 {
-	assert(m_currentScope);
+	if (asserts(m_currentScope))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Closed non-existing scope."));
 	m_currentScope = m_currentScope->getEnclosingScope();
 }
 
 void DeclarationRegistrationHelper::registerDeclaration(Declaration& _declaration, bool _opensScope)
 {
-	assert(m_currentScope);
+	if (asserts(m_currentScope))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Declaration registered without scope."));
 	if (!m_currentScope->registerDeclaration(_declaration))
 		BOOST_THROW_EXCEPTION(DeclarationError() << errinfo_sourceLocation(_declaration.getLocation())
 												 << errinfo_comment("Identifier already declared."));
@@ -177,7 +180,8 @@ void ReferencesResolver::endVisit(VariableDeclaration& _variable)
 
 bool ReferencesResolver::visit(Return& _return)
 {
-	assert(m_returnParameters);
+	if (asserts(m_returnParameters))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Return parameters not set."));
 	_return.setFunctionReturnParameters(*m_returnParameters);
 	return true;
 }
diff --git a/libsolidity/Scanner.cpp b/libsolidity/Scanner.cpp
index d8defb50a..c36820317 100644
--- a/libsolidity/Scanner.cpp
+++ b/libsolidity/Scanner.cpp
@@ -50,7 +50,6 @@
  * Solidity scanner.
  */
 
-#include <cassert>
 #include <algorithm>
 #include <tuple>
 #include <libsolidity/Scanner.h>
@@ -113,11 +112,10 @@ void Scanner::reset(CharStream const& _source)
 }
 
 
-bool Scanner::scanHexNumber(char& o_scannedNumber, int _expectedLength)
+bool Scanner::scanHexByte(char& o_scannedByte)
 {
-	assert(_expectedLength <= 4);  // prevent overflow
 	char x = 0;
-	for (int i = 0; i < _expectedLength; i++)
+	for (int i = 0; i < 2; i++)
 	{
 		int d = HexValue(m_char);
 		if (d < 0)
@@ -128,7 +126,7 @@ bool Scanner::scanHexNumber(char& o_scannedNumber, int _expectedLength)
 		x = x * 16 + d;
 		advance();
 	}
-	o_scannedNumber = x;
+	o_scannedByte = x;
 	return true;
 }
 
@@ -175,7 +173,8 @@ Token::Value Scanner::skipSingleLineComment()
 
 Token::Value Scanner::skipMultiLineComment()
 {
-	assert(m_char == '*');
+	if (asserts(m_char == '*'))
+		BOOST_THROW_EXCEPTION(InternalCompilerError());
 	advance();
 	while (!isSourcePastEndOfInput())
 	{
@@ -418,15 +417,11 @@ bool Scanner::scanEscape()
 	case 't':
 		c = '\t';
 		break;
-	case 'u':
-		if (!scanHexNumber(c, 4))
-			return false;
-		break;
 	case 'v':
 		c = '\v';
 		break;
 	case 'x':
-		if (!scanHexNumber(c, 2))
+		if (!scanHexByte(c))
 			return false;
 		break;
 	}
@@ -468,7 +463,9 @@ void Scanner::scanDecimalDigits()
 
 Token::Value Scanner::scanNumber(bool _periodSeen)
 {
-	assert(IsDecimalDigit(m_char));  // the first digit of the number or the fraction
+	// the first digit of the number or the fraction
+	if (asserts(IsDecimalDigit(m_char)))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Number does not start with decimal digit."));
 	enum { DECIMAL, HEX, OCTAL, IMPLICIT_OCTAL, BINARY } kind = DECIMAL;
 	LiteralScope literal(this);
 	if (_periodSeen)
@@ -510,7 +507,8 @@ Token::Value Scanner::scanNumber(bool _periodSeen)
 	// scan exponent, if any
 	if (m_char == 'e' || m_char == 'E')
 	{
-		assert(kind != HEX);  // 'e'/'E' must be scanned as part of the hex number
+		if (asserts(kind != HEX)) // 'e'/'E' must be scanned as part of the hex number
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
 		if (kind != DECIMAL) return Token::ILLEGAL;
 		// scan exponent
 		addLiteralCharAndAdvance();
@@ -606,7 +604,8 @@ Token::Value Scanner::scanNumber(bool _periodSeen)
 
 static Token::Value KeywordOrIdentifierToken(string const& input)
 {
-	assert(!input.empty());
+	if (asserts(!input.empty()))
+		BOOST_THROW_EXCEPTION(InternalCompilerError());
 	int const kMinLength = 2;
 	int const kMaxLength = 10;
 	if (input.size() < kMinLength || input.size() > kMaxLength)
@@ -634,7 +633,8 @@ case ch:
 
 Token::Value Scanner::scanIdentifierOrKeyword()
 {
-	assert(IsIdentifierStart(m_char));
+	if (asserts(IsIdentifierStart(m_char)))
+		BOOST_THROW_EXCEPTION(InternalCompilerError());
 	LiteralScope literal(this);
 	addLiteralCharAndAdvance();
 	// Scan the rest of the identifier characters.
@@ -656,7 +656,8 @@ char CharStream::advanceAndGet()
 
 char CharStream::rollback(size_t _amount)
 {
-	assert(m_pos >= _amount);
+	if (asserts(m_pos >= _amount))
+		BOOST_THROW_EXCEPTION(InternalCompilerError());
 	m_pos -= _amount;
 	return get();
 }
diff --git a/libsolidity/Scanner.h b/libsolidity/Scanner.h
index c2dfb476f..537c2434e 100644
--- a/libsolidity/Scanner.h
+++ b/libsolidity/Scanner.h
@@ -169,7 +169,7 @@ private:
 	/// If the next character is _next, advance and return _then, otherwise return _else.
 	inline Token::Value selectToken(char _next, Token::Value _then, Token::Value _else);
 
-	bool scanHexNumber(char& o_scannedNumber, int _expectedLength);
+	bool scanHexByte(char& o_scannedByte);
 
 	/// Scans a single JavaScript token.
 	void scanToken();
diff --git a/libsolidity/Token.h b/libsolidity/Token.h
index c54f387c7..0fb9b670f 100644
--- a/libsolidity/Token.h
+++ b/libsolidity/Token.h
@@ -42,9 +42,9 @@
 
 #pragma once
 
-#include <cassert>
 #include <libdevcore/Common.h>
 #include <libdevcore/Log.h>
+#include <libsolidity/Exceptions.h>
 
 namespace dev
 {
@@ -81,8 +81,6 @@ namespace solidity
 	T(SEMICOLON, ";", 0)                                               \
 	T(PERIOD, ".", 0)                                                  \
 	T(CONDITIONAL, "?", 3)                                             \
-	T(INC, "++", 0)                                                    \
-	T(DEC, "--", 0)                                                    \
 	T(ARROW, "=>", 0)                                                  \
 	\
 	/* Assignment operators. */                                        \
@@ -136,6 +134,8 @@ namespace solidity
 	/* being contiguous and sorted in the same order! */               \
 	T(NOT, "!", 0)                                                     \
 	T(BIT_NOT, "~", 0)                                                 \
+	T(INC, "++", 0)                                                    \
+	T(DEC, "--", 0)                                                    \
 	K(DELETE, "delete", 0)                                             \
 	\
 	/* Keywords */                                                     \
@@ -224,7 +224,8 @@ public:
 	// (e.g. "LT" for the token LT).
 	static char const* getName(Value tok)
 	{
-		assert(tok < NUM_TOKENS);  // tok is unsigned
+		if (asserts(tok < NUM_TOKENS))
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
 		return m_name[tok];
 	}
 
@@ -249,55 +250,10 @@ public:
 			   isEqualityOp(op) || isInequalityOp(op);
 	}
 
-	static Value negateCompareOp(Value op)
-	{
-		assert(isArithmeticCompareOp(op));
-		switch (op)
-		{
-		case EQ:
-			return NE;
-		case NE:
-			return EQ;
-		case LT:
-			return GTE;
-		case GT:
-			return LTE;
-		case LTE:
-			return GT;
-		case GTE:
-			return LT;
-		default:
-			assert(false); // should not get here
-			return op;
-		}
-	}
-
-	static Value reverseCompareOp(Value op)
-	{
-		assert(isArithmeticCompareOp(op));
-		switch (op)
-		{
-		case EQ:
-			return EQ;
-		case NE:
-			return NE;
-		case LT:
-			return GT;
-		case GT:
-			return LT;
-		case LTE:
-			return GTE;
-		case GTE:
-			return LTE;
-		default:
-			assert(false); // should not get here
-			return op;
-		}
-	}
-
 	static Value AssignmentToBinaryOp(Value op)
 	{
-		assert(isAssignmentOp(op) && op != ASSIGN);
+		if (asserts(isAssignmentOp(op) && op != ASSIGN))
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
 		return Token::Value(op + (BIT_OR - ASSIGN_BIT_OR));
 	}
 
@@ -311,7 +267,8 @@ public:
 	// have a (unique) string (e.g. an IDENTIFIER).
 	static char const* toString(Value tok)
 	{
-		assert(tok < NUM_TOKENS);  // tok is unsigned.
+		if (asserts(tok < NUM_TOKENS))
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
 		return m_string[tok];
 	}
 
@@ -319,7 +276,8 @@ public:
 	// operators; returns 0 otherwise.
 	static int precedence(Value tok)
 	{
-		assert(tok < NUM_TOKENS);  // tok is unsigned.
+		if (asserts(tok < NUM_TOKENS))
+			BOOST_THROW_EXCEPTION(InternalCompilerError());
 		return m_precedence[tok];
 	}
 
diff --git a/libsolidity/Types.cpp b/libsolidity/Types.cpp
index 4f5563391..a4d70e3a0 100644
--- a/libsolidity/Types.cpp
+++ b/libsolidity/Types.cpp
@@ -20,7 +20,6 @@
  * Solidity data types
  */
 
-#include <cassert>
 #include <libdevcore/CommonIO.h>
 #include <libdevcore/CommonData.h>
 #include <libsolidity/Types.h>
@@ -33,6 +32,9 @@ namespace solidity
 
 std::shared_ptr<Type> Type::fromElementaryTypeName(Token::Value _typeToken)
 {
+	if (asserts(Token::isElementaryTypeName(_typeToken)))
+		BOOST_THROW_EXCEPTION(InternalCompilerError());
+
 	if (Token::INT <= _typeToken && _typeToken <= Token::HASH256)
 	{
 		int offset = _typeToken - Token::INT;
@@ -52,7 +54,8 @@ std::shared_ptr<Type> Type::fromElementaryTypeName(Token::Value _typeToken)
 	else if (_typeToken == Token::BOOL)
 		return std::make_shared<BoolType>();
 	else
-		assert(false); // @todo add other tyes
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unable to convert elementary typename " +
+																		 std::string(Token::toString(_typeToken)) + " to type."));
 	return std::shared_ptr<Type>();
 }
 
@@ -63,7 +66,7 @@ std::shared_ptr<Type> Type::fromUserDefinedTypeName(UserDefinedTypeName const& _
 
 std::shared_ptr<Type> Type::fromMapping(Mapping const&)
 {
-	assert(false); //@todo not yet implemented
+	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Mapping types not yet implemented."));
 	return std::shared_ptr<Type>();
 }
 
@@ -94,7 +97,8 @@ IntegerType::IntegerType(int _bits, IntegerType::Modifier _modifier):
 {
 	if (isAddress())
 		_bits = 160;
-	assert(_bits > 0 && _bits <= 256 && _bits % 8 == 0);
+	if (asserts(_bits > 0 && _bits <= 256 && _bits % 8 == 0))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid bit number for integer type: " + dev::toString(_bits)));
 }
 
 bool IntegerType::isImplicitlyConvertibleTo(Type const& _convertTo) const
@@ -187,7 +191,7 @@ u256 BoolType::literalValue(Literal const& _literal) const
 	else if (_literal.getToken() == Token::FALSE_LITERAL)
 		return u256(0);
 	else
-		assert(false);
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Bool type constructed from non-boolean literal."));
 }
 
 bool ContractType::operator==(Type const& _other) const
diff --git a/libsolidity/Types.h b/libsolidity/Types.h
index 190134d7a..4493b8037 100644
--- a/libsolidity/Types.h
+++ b/libsolidity/Types.h
@@ -26,6 +26,7 @@
 #include <string>
 #include <boost/noncopyable.hpp>
 #include <libdevcore/Common.h>
+#include <libsolidity/Exceptions.h>
 #include <libsolidity/ASTForward.h>
 #include <libsolidity/Token.h>
 
@@ -75,7 +76,11 @@ public:
 	virtual unsigned getCalldataEncodedSize() const { return 0; }
 
 	virtual std::string toString() const = 0;
-	virtual u256 literalValue(Literal const&) const { assert(false); }
+	virtual u256 literalValue(Literal const&) const
+	{
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Literal value requested "
+																		  "for type without literals."));
+	}
 };
 
 /**
diff --git a/solc/main.cpp b/solc/main.cpp
index 1cf466c72..04fee2905 100644
--- a/solc/main.cpp
+++ b/solc/main.cpp
@@ -84,21 +84,27 @@ int main(int argc, char** argv)
 	ASTPointer<ContractDefinition> ast;
 	shared_ptr<Scanner> scanner = make_shared<Scanner>(CharStream(sourceCode));
 	Parser parser;
+	bytes instructions;
+	Compiler compiler;
 	try
 	{
 		ast = parser.parse(scanner);
+
+		NameAndTypeResolver resolver;
+		resolver.resolveNamesAndTypes(*ast.get());
+
+		cout << "Syntax tree for the contract:" << endl;
+		dev::solidity::ASTPrinter printer(ast, sourceCode);
+		printer.print(cout);
+
+		compiler.compileContract(*ast);
+		instructions = compiler.getAssembledBytecode();
 	}
 	catch (ParserError const& exception)
 	{
 		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Parser error", *scanner);
 		return -1;
 	}
-
-	NameAndTypeResolver resolver;
-	try
-	{
-		resolver.resolveNamesAndTypes(*ast.get());
-	}
 	catch (DeclarationError const& exception)
 	{
 		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Declaration error", *scanner);
@@ -109,23 +115,26 @@ int main(int argc, char** argv)
 		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Type error", *scanner);
 		return -1;
 	}
-
-	cout << "Syntax tree for the contract:" << endl;
-	dev::solidity::ASTPrinter printer(ast, sourceCode);
-	printer.print(cout);
-
-	bytes instructions;
-	Compiler compiler;
-	try
-	{
-		compiler.compileContract(*ast);
-		instructions = compiler.getAssembledBytecode();
-	}
 	catch (CompilerError const& exception)
 	{
 		SourceReferenceFormatter::printExceptionInformation(cerr, exception, "Compiler error", *scanner);
 		return -1;
 	}
+	catch (InternalCompilerError const& exception)
+	{
+		cerr << "Internal compiler error: " << boost::diagnostic_information(exception) << endl;
+		return -1;
+	}
+	catch (Exception const& exception)
+	{
+		cerr << "Exception during compilation: " << boost::diagnostic_information(exception) << endl;
+		return -1;
+	}
+	catch (...)
+	{
+		cerr << "Unknown exception during compilation." << endl;
+		return -1;
+	}
 
 	cout << "EVM assembly:" << endl;
 	compiler.streamAssembly(cout);