My questions result from the observation that in the virtual dtor of enable_shared_from_this, I tried BOOST_ASSERT( _shared_count.empty() ), but this makes 3 tests fail. Looking at these tests, I don't see why they should be legal: In esft_constructor_test.cpp, line 143, X initializes early_px by calling shared_from_this, but X is never passed to a shared_ptr which then owns it. From what I understand, this should be illegal. The next problem is esft_constructor_test.cpp, line 160. y.shared_from_this() returns a shared_ptr, but again, no shared_ptr takes ownership of Y later. While shared_from_this() is not called from the ctor, I wonder if this is yet another use case or just an accident. The test case in shared_from_this_test.cpp, line 135 is similar. Regards, Daniel