Getting mildew off wood ceiling.. any solution??

I have dark wood ceilings in my house, not sure what kind of wood but again very dark with an almost red tone. In the bathroom there is significant mold, since the wood is so dark it's hard to tell, but it looks black and is in patches. I know I need to get a better ventilating system in there but does anyone know an easy, quick way to get rid of it? It's been there for years, just moved in with a friend and she's never bothered to take care of it. thanks!