Taking a cue from Microsoft, the Gateses place safe bets while also taking risks. On the safer side, notes Schwab, is their commitment of over $1.5 billion to distribute proven vaccines to children in developing countries. On the riskier end is the $450 million the foundation has committed to funding research on new vaccines and technologies.

Inspiring governments to pitch in and pay attention may ultimately be one of the Gateses' greatest contributions, not only in global health but also in education. Their foundation has helped highlight the problem of high school dropouts at a time when most educators were talking about low minority test scores. Now, says William Porter, executive director of Grantmakers for Education, "a lot more people are talking about the ones who drop out before they even take the test."

Bill BORN: Oct. 28, 1955 EDUCATION: Dropped out of Harvard University his junior year to devote his energies to Microsoft FAMILY: With Melinda, three children Melinda BORN: Aug. 15, 1964 EDUCATION: B.S., Duke University; M.B.A., Fuqua School of Business OCCUPATIONAL HAZARD: "Bill's joke these days is that when people see him coming at cocktail parties they run because they know he's going to talk about tuberculosis."