Microsoft co-founder Paul Allen has pledged to donate the majority of his $13.5 billion fortune to charity. Allen's pledge came just weeks after his former business partner, Bill Gates, and legendary investor Warren Buffet both called on other billionaires to commit to giving away at least half their fortunes. "I want to announce that my philanthropic efforts will continue after my lifetime," said Allen, who has already given about $1 billion to charity over the years.

"I've planned for many years now that the majority of my estate will be left to philanthropy to continue the work of the foundation and fund non-profit scientific research." "As our philanthropy continues in the years ahead, we will look for new opportunities to make a difference in the lives of future generations," said Allen, 57, in the statement.

Allen is the 37th richest man in the world, with $13.5 billion in assets, according to Forbes magazine. He founded Microsoft together with Gates in 1975 and left the company in 1983. Allen was diagnosed in November with non-Hodgkin's lymphoma and began chemotherapy.