Hi, Looking through the documentation of Boost.Variant (both 1.31 and cvs versions), I see that "variant is itself LessThanComparable if and only if every one of its bounded types meets the requirements of the concept". The documentation directly hyper-links to the concept part of Boost and this concept description explains that "LessThanComparable types must have <, >, <=, and >= operators". Unfortunately, boost::variant implementation only defines operator<. So here we have a contradiction between the implementation and the interface. The same kind of problem arises with operator!= and the EqualityComparable concept. I am not sure what the best solution is: - define the missing operators in boost::variant, - remove any reference to LessThanComparable and EqualityComparable concepts from boost::variant documentation, - correct the concepts so they only speak about operator< and operator==. The last solution corresponds to the way the concepts are defined in the [lib.utilities] part of the C++ standard. But I would rather see the missing operators defined in boost::variant if possible. Regards, Guillaume