you have to have a medicham and trade it with the girl in snowpoint town for a haunter
You trade haunter to get gengar.
Haunter evolves when traded
Are you plain stupid!?!HAUNTER EVOLVES ONLY IN TRADES!
Haunter will only evolve when you trade it with someone.
Some lady in a city will trade you it but it will stay as haunter.
Maybe
Haunter evolves only by trading to another game.
Actually, Haunter does evolve. Its evolves into Gengar when you trade it.
Nothing, to evolve haunter you have to trade him...
You trade Haunter to another Diamond, Pearl, or Platinum version and it will evolve into a Gengar. You will need to trade back to your original Diamond game to get the Gengar. Hope I helped, bye
25 into Haunter and then if u trade Haunter he evolves into Gengar
you get it over a trade.