Check out Eva, Jessica, Beyonce and more and vote on who looks best – then take PEOPLE's ultimate bathing-suit poll and see the results in the Summer StyleWatch issue, on newsstands May 12. By Serena Kappes
You'd never know it, but the petite actress says she's "extremely lazy" about exercising. Wearing skimpy clothes on Desperate Housewives prompted Longoria (31, in Hollywood) to hire a personal trainer and eat right (egg whites, nonfat yogurt) on the set. Still, she admits, "On my days off I'm not so healthy."
To fit into her Daisy Duke shorts, Simpson, 25, dieted for two months and worked out six days a week. "When I found out I got the role, I went straight to the gym," says the singer-actress (in Hawaii), who toned up with squats, lunges and weight-resistance exercises. She's since eased up on the workouts but has kept her lean shape.
Having to wear a bikini is a great motivator – just ask Alba, 24. "I work out more when I'm going to be photographed in a bathing suit," she admits. In fact, the actress (in Los Cabos, Mexico) sweats to Tae Bo and hits the elliptical machine to make sure she's always camera-ready.
No wonder her nickname is the Body: At 41 and after two children – sons Flynn, 8, and Aurelius, 3 – the Australian supermodel (in Barbados) still makes waves. The long-limbed former catwalker even showed off her shape in the pages of Sports Illustrated's annual swimsuit issue recently.
It's all about balance for Aniston, 37, who stays trim on the Zone diet (which regulates the amount of fats, carbs and proteins in each meal) but also loves Mexican food. And she exercises three or four times weekly, including doing Pilates. "I just love it," the actress (in France) says. "I feel the shift in my back and lower back. My body is tweaked."