The correct is: взаимный фонд.

P.S. 1 : Can someone explain me why the forum didn't work today. I was wondering if there is a possibility the forum to be totally destroyed. I don't want to lose the archive with your answers, for me is like a russian language guidebook.

P.S. 2: The greatest investor of all times Warren Buffet says that index mutual funds is the supreme investment vehicle.