diff --git a/SConstruct b/SConstruct
index 14471787e0..c238dc3d77 100644
--- a/SConstruct
+++ b/SConstruct
@@ -1010,6 +1010,7 @@ env.Append(
 		"-DIE_CORE_MINORVERSION=$IECORE_MINOR_VERSION",
 		"-DIE_CORE_PATCHVERSION=$IECORE_PATCH_VERSION",
 		"-DBOOST_FILESYSTEM_VERSION=3",
+		"-DBOOST_FILESYSTEM_NO_DEPRECATED",
 	]
 )
 
diff --git a/src/IECore/DeepImageWriter.cpp b/src/IECore/DeepImageWriter.cpp
index fd0426f53c..c2daa88a5e 100644
--- a/src/IECore/DeepImageWriter.cpp
+++ b/src/IECore/DeepImageWriter.cpp
@@ -146,7 +146,7 @@ void DeepImageWriter::registerDeepImageWriter( const std::string &extensions, Ca
 
 DeepImageWriterPtr DeepImageWriter::create( const std::string &fileName )
 {
-	std::string ext = boost::filesystem::extension( boost::filesystem::path( fileName ) );
+	std::string ext = boost::filesystem::path( fileName ).extension();
 
 	ExtensionsToFnsMap *m = extensionsToFns();
 	ExtensionsToFnsMap::const_iterator it = m->find( ext );
diff --git a/src/IECore/FileNameParameter.cpp b/src/IECore/FileNameParameter.cpp
index a82337c6d0..03c183e74d 100644
--- a/src/IECore/FileNameParameter.cpp
+++ b/src/IECore/FileNameParameter.cpp
@@ -1,6 +1,6 @@
 //////////////////////////////////////////////////////////////////////////
 //
-//  Copyright (c) 2007-2010, Image Engine Design Inc. All rights reserved.
+//  Copyright (c) 2007-2013, Image Engine Design Inc. All rights reserved.
 //
 //  Redistribution and use in source and binary forms, with or without
 //  modification, are permitted provided that the following conditions are
@@ -86,7 +86,7 @@ bool FileNameParameter::valueValid( const Object *value, std::string *reason ) c
 	// extensions check
 	if( extensions().size() )
 	{
-		string ext = boost::filesystem::extension(boost::filesystem::path( s->readable()));
+		string ext = boost::filesystem::path( s->readable() ).extension();
 
 		const vector<string> &exts = extensions();
 		bool found = false;
diff --git a/src/IECore/FileSequenceFunctions.cpp b/src/IECore/FileSequenceFunctions.cpp
index 0e9b5adddd..be5834665a 100644
--- a/src/IECore/FileSequenceFunctions.cpp
+++ b/src/IECore/FileSequenceFunctions.cpp
@@ -64,6 +64,20 @@
 
 #endif
 
+#if BOOST_VERSION < 104400
+
+	// Boost 1.44.0 introduced Filesystem v3, which we use by defining BOOST_FILESYSTEM_VERSION=3 via
+	// the build process. Prior versions of boost didn't have this version, so we need this define
+	// to help write code suitable for both.
+	
+	#define PATH_TO_STRING filename()
+
+#else
+
+	#define PATH_TO_STRING filename().string()
+	
+#endif
+
 using namespace IECore;
 
 void IECore::findSequences( const std::vector< std::string > &names, std::vector< FileSequencePtr > &sequences, size_t minSequenceSize )
@@ -181,7 +195,7 @@ void IECore::ls( const std::string &path, std::vector< FileSequencePtr > &sequen
 	 	std::vector< std::string > files;
 		for ( boost::filesystem::directory_iterator it( path ); it != end; ++it )
 		{
-			files.push_back( it->path().filename().string() );
+			files.push_back( it->path().PATH_TO_STRING );
 		}
 
 		findSequences( files, sequences, minSequenceSize );
@@ -203,9 +217,9 @@ void IECore::ls( const std::string &sequencePath, FileSequencePtr &sequence, siz
 
  	std::vector< std::string > files;
 
-	boost::filesystem::path dir = boost::filesystem::path( sequencePath ).branch_path();
+	boost::filesystem::path dir = boost::filesystem::path( sequencePath ).parent_path();
 
-	std::string baseSequencePath = boost::filesystem::path( sequencePath ).filename().string();
+	std::string baseSequencePath = boost::filesystem::path( sequencePath ).PATH_TO_STRING;
 
 	const std::string::size_type first = baseSequencePath.find_first_of( '#' );
 	assert( first != std::string::npos );
@@ -225,7 +239,7 @@ void IECore::ls( const std::string &sequencePath, FileSequencePtr &sequence, siz
 
 	for ( boost::filesystem::directory_iterator it( dirToCheck ); it != end; ++it )
 	{
-		const std::string fileName = it->path().filename().string();
+		const std::string fileName = it->path().PATH_TO_STRING;
 
 		if ( fileName.size() >= std::min( prefix.size(), suffix.size() ) && fileName.substr( 0, prefix.size() ) == prefix && fileName.substr( fileName.size() - suffix.size(), suffix.size() ) == suffix )
 		{
diff --git a/src/IECore/FileSequenceParameter.cpp b/src/IECore/FileSequenceParameter.cpp
index 48dff2a006..6f1c9229ac 100644
--- a/src/IECore/FileSequenceParameter.cpp
+++ b/src/IECore/FileSequenceParameter.cpp
@@ -1,6 +1,6 @@
 //////////////////////////////////////////////////////////////////////////
 //
-//  Copyright (c) 2009-2010, Image Engine Design Inc. All rights reserved.
+//  Copyright (c) 2009-2013, Image Engine Design Inc. All rights reserved.
 //
 //  Redistribution and use in source and binary forms, with or without
 //  modification, are permitted provided that the following conditions are
@@ -128,7 +128,7 @@ bool FileSequenceParameter::valueValid( const Object *value, std::string *reason
 
 	if ( m_extensions.size() )
 	{
-		std::string ext = boost::filesystem::extension( boost::filesystem::path( fileSequence->getFileName() ) );
+		std::string ext = boost::filesystem::path( fileSequence->getFileName() ).extension();
 		if ( ext.size() && ext[0] == '.' )
 		{
 			ext = ext.substr( 1, ext.size() - 1 );
diff --git a/src/IECore/FileSequenceVectorParameter.cpp b/src/IECore/FileSequenceVectorParameter.cpp
index 65f667b285..fc823043a1 100644
--- a/src/IECore/FileSequenceVectorParameter.cpp
+++ b/src/IECore/FileSequenceVectorParameter.cpp
@@ -1,6 +1,6 @@
 //////////////////////////////////////////////////////////////////////////
 //
-//  Copyright (c) 2009-2010, Image Engine Design Inc. All rights reserved.
+//  Copyright (c) 2009-2013, Image Engine Design Inc. All rights reserved.
 //
 //  Redistribution and use in source and binary forms, with or without
 //  modification, are permitted provided that the following conditions are
@@ -129,7 +129,7 @@ bool FileSequenceVectorParameter::valueValid( const Object *value, std::string *
 
 		if ( m_extensions.size() )
 		{
-			std::string ext = boost::filesystem::extension( boost::filesystem::path( fileSequence->getFileName() ) );
+			std::string ext = boost::filesystem::path( fileSequence->getFileName() ).extension();
 			if ( ext.size() && ext[0] == '.' )
 			{
 				ext = ext.substr( 1, ext.size() - 1 );
diff --git a/src/IECore/IndexedIO.cpp b/src/IECore/IndexedIO.cpp
index f52a0cb080..471073d81a 100644
--- a/src/IECore/IndexedIO.cpp
+++ b/src/IECore/IndexedIO.cpp
@@ -53,7 +53,7 @@ IndexedIOPtr IndexedIO::create( const std::string &path, const IndexedIO::EntryI
 {
 	IndexedIOPtr result = 0;
 
-	std::string extension = fs::extension(path);
+	std::string extension = fs::path( path ).extension();
 
 	const CreatorMap &createFns = getCreateFns();
 
diff --git a/src/IECore/Reader.cpp b/src/IECore/Reader.cpp
index 59a122fd68..92a27555a3 100644
--- a/src/IECore/Reader.cpp
+++ b/src/IECore/Reader.cpp
@@ -1,6 +1,6 @@
 //////////////////////////////////////////////////////////////////////////
 //
-//  Copyright (c) 2007-2010, Image Engine Design Inc. All rights reserved.
+//  Copyright (c) 2007-2013, Image Engine Design Inc. All rights reserved.
 //
 //  Redistribution and use in source and binary forms, with or without
 //  modification, are permitted provided that the following conditions are
@@ -79,7 +79,7 @@ ReaderPtr Reader::create( const std::string &fileName )
 	bool knownExtension = false;
 	ExtensionsToFnsMap *m = extensionsToFns();
 	assert( m );
-	string ext = extension(boost::filesystem::path(fileName));
+	string ext = boost::filesystem::path( fileName ).extension();
 	if( ext!="" )
 	{
 		ExtensionsToFnsMap::const_iterator it = m->find( ext );
diff --git a/src/IECore/SceneInterface.cpp b/src/IECore/SceneInterface.cpp
index 1da2e0efce..ed34833633 100644
--- a/src/IECore/SceneInterface.cpp
+++ b/src/IECore/SceneInterface.cpp
@@ -99,7 +99,7 @@ SceneInterfacePtr SceneInterface::create( const std::string &path, IndexedIO::Op
 {
 	SceneInterfacePtr result = 0;
 
-	std::string extension = boost::filesystem::extension(path);
+	std::string extension = boost::filesystem::path( path ).extension();
 	IndexedIO::OpenModeFlags openMode = IndexedIO::OpenModeFlags( mode & (IndexedIO::Read|IndexedIO::Write|IndexedIO::Append) );
 	std::pair< std::string, IndexedIO::OpenModeFlags > key( extension, openMode );
 
diff --git a/src/IECore/TGAImageReader.cpp b/src/IECore/TGAImageReader.cpp
index a86bc0d696..4815fb7a4e 100644
--- a/src/IECore/TGAImageReader.cpp
+++ b/src/IECore/TGAImageReader.cpp
@@ -107,7 +107,7 @@ bool TGAImageReader::canRead( const string &fileName )
 	}
 	
 	/// No magic number for v1 files, so just check the extension
-	return boost::filesystem::extension( fileName ) == ".tga";
+	return boost::filesystem::path( fileName ).extension() == ".tga";
 }
 
 void TGAImageReader::channelNames( vector<string> &names )
diff --git a/src/IECore/Writer.cpp b/src/IECore/Writer.cpp
index 772154932a..89e570a0fe 100644
--- a/src/IECore/Writer.cpp
+++ b/src/IECore/Writer.cpp
@@ -115,7 +115,7 @@ void Writer::registerWriter( const std::string &extensions, CanWriteFn canWrite,
 
 WriterPtr Writer::create( ObjectPtr object, const std::string &fileName )
 {
-	string ext = extension(boost::filesystem::path(fileName));
+	string ext = boost::filesystem::path( fileName ).extension();
 
 	ExtensionsToFnsMap *m = extensionsToFns();
 	assert( m );
@@ -145,7 +145,7 @@ WriterPtr Writer::create( ObjectPtr object, const std::string &fileName )
 
 WriterPtr Writer::create( const std::string &fileName )
 {
-	string ext = extension(boost::filesystem::path(fileName));
+	string ext = boost::filesystem::path( fileName ).extension();
 
 	ExtensionsToFnsMap *m = extensionsToFns();
 	ExtensionsToFnsMap::const_iterator it = m->find( ext );
diff --git a/src/IECoreRI/SHWDeepImageWriter.cpp b/src/IECoreRI/SHWDeepImageWriter.cpp
index 92d096d9fa..c8026690b6 100644
--- a/src/IECoreRI/SHWDeepImageWriter.cpp
+++ b/src/IECoreRI/SHWDeepImageWriter.cpp
@@ -1,6 +1,6 @@
 //////////////////////////////////////////////////////////////////////////
 //
-//  Copyright (c) 2012, Image Engine Design Inc. All rights reserved.
+//  Copyright (c) 2012-2013, Image Engine Design Inc. All rights reserved.
 //
 //  Redistribution and use in source and binary forms, with or without
 //  modification, are permitted provided that the following conditions are
@@ -83,7 +83,7 @@ bool SHWDeepImageWriter::canWrite( const std::string &fileName )
 	
 	int status = DTEX_NOFILE;
 	
-	std::string ext = boost::filesystem::extension( boost::filesystem::path( fileName ) );
+	std::string ext = boost::filesystem::path( fileName ).extension();
 	if ( ext == ".shw" )
 	{
 		status = DtexCreateFile( fileName.c_str(), dtexCache, &dtexFile );