... No formats are completely different. (Hammer uses '.vmf' while Gtk uses '.map' (Also checked the content of a '.vmf' comletely different to '.map' files) and the '.bsp' i doubt will work either even assuming someone set up the entities) My question to you is: WHY!??!?! Gtk Radiant is far easier to use then Hammer (imo (I have used both)), how could you want to use it?