<iostream> is the only C++ header that extracts a cost simply by including it (in typical implementations). The usual implementation is for it to include a static object of type std::ios_base::Init which is responsible for initializing the 8 terminal streams (cin, cout, cerr, clog, wcin, wcout, wcerr, wclog). I've always thought it good programming practice to avoid including <iostream> if the translation unit didn't actually need one of these 8 terminal streams. For example if I needed to just get to istream and ostream to write my own I/O I would include <istream> and <ostream> but not <iostream> (the naming is very unfortunate). It has recently come to my attention that I could be overly sensitive to this issue and making a fuss about nothing. So I'm writing here for a reality check. Do boost programmers consider the use of <iostream> as a short cut to get to non-terminal-streams I/O a reasonable technique? Or do boost programmers feel that use of <iostream> should be reserved only when using one or more of cin, cout, cerr, clog, wcin, wcout, wcerr, wclog? I did a brief survey of boost 1.33.1 and found many "relaxed" uses of <iostream> under the boost/ directory (i.e. non test-case code). So in practice it does appear that using <iostream> as a shortcut is considered acceptable practice. However I wanted to highlight the point just in case people do view this as a bug that has simply snuck in under the radar to date. -Howard