Peter, I've been expecting for some time that you were going to put the placeholders in a sub-namespace of boost, if only to avoid the ODR violations it is currently causing. No? The fact that I have to write mpl::_1 just to avoid colliding with <unnamed>::_1 is disconcerting at best. If another library came along and did what boost/bind/placeholders.hpp does, it would cause a clash. My suggestion, assuming you care about backwards compatibility, is: boost/bind/placeholders.hpp declares placeholders in namespace boost::bind::placeholders. boost/bind/bind.hpp has the current contents of boost/bind.hpp, except that placeholders are not declared in the <unnamed>:: boost/bind.hpp #include <boost/bind/bind.hpp> #include <boost/bind/placeholders.hpp> namespace { using namespace boost::bind::placeholders; } Is something wrong with that? -- Dave Abrahams Boost Consulting http://www.boost-consulting.com