Company: WellPoint
Fortune 500 rank: 42
First year as CEO: 2007
Most Powerful Women rank: 5
Braly's reach is unquestionable: With 34 million members, health insurer WellPoint touches one in nine Americans covered. Now she's tapping into the Medicare market with the purchase of senior health care provider CareMore. Her challenge: translating customer growth into higher profits.
NEXT: Carol Meyrowitz