However, I am NOT (yet) an expert in the Iostreams library so please excuse me if I am missing something obvious. I add 2 sinks filtering_ostream out; out.push(file_sink("Report.txt")); out.push(cout); I get an exception thrown on the second one (regardless of which one goes in first) In searching the archives, I noticed this mail: http://tinyurl.com/6soeb where Johnathon Turkis writes: "For this we need to define an OutputFilter which stores a reference to an ostream and has a member function 'write' which forwards all characters to the stored ostream as well as to the downstream sink (you don't need to understand the following code -- the point is that it's just a few lines): struct tee : boost::io::output_filter { tee(std::ostream& dest) : dest(dest) { } template<typename Sink> void write(Sink& snk, char* s, std::streamsize n) { // Write to the downstream Sink boost::io::write(snk, s, n); // Write to the stored ostream: dest.write(s, n); } std::ostream& dest; }; We use the tee as follows. Given two ostreams ostream first; ostream second; we define a filtering_ostream which passes data through the tee to both streams: filtering_ostream out; out.push(tee(first)); out.push(second); out << "this gets written to both ostreams\n"; " Which looks "good" except I suspect the library has changed since the above is not compiling for me under VC71. (it complains about wanting a Put() instead of a write()).. Any help appreciated- and also - a request- if "tee" functionality could be officially implemented in the streaming lib for output sinks. OR if it already is, I request that how do to it be spelled out more clearly in the documentation. Thanks Brian Braatz