(FORTUNE Magazine) – Cheers to diversity! In addition to perennial stalwarts Andrea Jung and Oprah Winfrey (Nos. 3 and 7, respectively), five African-American and Asian women appear among the 13 newcomers and returnees on FORTUNE's power list: Christine Poon at Johnson & Johnson, Myrtle Potter at Genentech, Jenny Ming at Old Navy, Ursula Burns at Xerox, and Ann Fudge, the new CEO of Young & Rubicam. That's impressive given that winning a spot on this list just keeps getting more difficult. When we launched it in 1998, heading a $3 billion business practically guaranteed inclusion. That's not so anymore. Just to maintain rank on the list, in fact, a woman has to gain power. Though Procter & Gamble diaper queen Deb Henretta had a terrific 2003, for example, she appears at No. 34--her same rank as last year.

How do we judge the candidates? We limit the pool to women in for-profit businesses, and we consider four key criteria: the size and importance of the woman's business in the global economy, her clout inside her company, the arc of her career (how quickly she has risen and where she's likely to go), and when appropriate, her influence on mass culture and society. The latter factor propels Gail Berman, our highest-ranking newcomer. The mother of reality television, Berman is key to Fox TV's rise to No. 1 in the ratings. Who made the biggest leaps? Two ladies from Citigroup: Marge Magner, the new CEO of its thriving consumer group, and Sallie Krawcheck, the new CEO of Smith Barney. To see where they are, just turn the page. --Patricia Sellers