(FORTUNE Magazine) – Bill Gates has decided to open up his wallet. As FORTUNE went to press, we learned that Microsoft's CEO had just given his two charitable foundations a combined gift of some $3.35 billion. Whoa! That's believed to be the largest charitable gift ever made. Gates gave some $2.23 billion to the William H. Gates Foundation, which parcels out grants for world health and human services, as well as for causes in the Seattle area. (The total assets of that foundation, which Gates established in 1994, are now $4.2 billion.) The world's richest man also gave the Gates Learning Foundation $1.12 billion, upping its assets to $1.3 billion. The Learning Foundation, formerly known as the Gates Library Foundation, provides libraries in low-income areas with software and computer services.

Gates, who has been criticized in the past regarding the level of his philanthropy, has maintained that he plans to give away the vast majority of his fortune, which is now valued in excess of $80 billion. Looks like he's stepping up to the plate.

--Andrew Serwer