"Bill and Melinda Gates have increased their foundation endowment over the course of the last two years, with enhancements of approximately $ 5 billion in each of the first three quarters of 1999," the foundation said in a statement yesterday.

The extra cash brings the foundation's total assets to more than $ 17 billion, the statement said. Gates is the founder of software mega corporation Microsoft. According to Forbes magazine, he is the planet's richest man with an estimated worth of $ 90 billion.

Gates' huge increase in wealth last year came largely from his Microsoft stock. For last year's ranking, Microsoft was trading at about $ 42 per share on the Nasdaq. Now it trades around $ 95.

Global health is a major focus of the foundation's activities.Recent gifts include $ 50 million toward a new vaccine for Malaria; $ 100 million for vaccines to children in developing countries, and $ 50 million administered by Columbia University to prevent maternal death in pregnancy and child birth in the poorest countries. Gates has given away more money to charity than any living American, according to the Foundation Center, which tracks charities.