SAN FRANCISCO: Facebook CEO Mark Zuckerberg reaped a $3.3 billion gain last year by exercising stock options in the social networking company that he founded in a Harvard University dorm room.

The windfall saddled Zuckerberg with a huge tax bill, even though he limited his Facebook salary to just $1, according to regulatory documents filed Monday.

It marks the second straight year that Zuckerberg has realized a huge gain on the holding that he has accumulated in Facebook Inc. since he started the company in 2004. In 2012, Zuckerberg made $2.3 billion off his stock options.