The following line in my Windows program: boost::filesystem::path my_path(my_filename, boost::filesystem::native); converts backslashes in my_filename to forward slashes, which means than when I use boost::filesystem::exists on the result, the file is reported as not existing even though it does. I notice the comments in boost::filesystem::m_path_append(), which is called by the constructor of boost::filesystem::path, say that this is what the function does, but this contradicts the documentation. http://boost.org/libs/filesystem/doc/portability_guide.htm says, of native: Side effect: Syntax for path constructor /src/ string is implementation defined according to the path syntax rules for the operating system. Use: In path constructors, when the source is operator input or other sources which are formatted according to operating system rules. I understand this to mean that boost::filesystem::native converts the file into the format required by the OS. I certainly would not expect it to make the format wrong if it is already correct. Is there something I've overlooked here, or is this a bug, or is the documentation wrong (or just misleading)? I'm puzzled. Paul