Yani Tseng is used to being at the top in 2011, and the beginning of the Walmart NW Arkansas Championship is no different.

Tseng, the world's top player and the tournament's defending champion, shot a five-under 66 on Friday to share the lead with Stacy Lewis after the first round of the three-day event.

After closing her round with an eagle, Tseng claimed her second 18-hole lead of the year and the fourth of her career. She went bogey-free on Friday, as did Lewis with five birdies, and will go for her third straight win when in such a situation.

"I was really patient today, and I had a great group," Tseng said of her playing partners, world No. 2 Suzann Pettersen and Ryann O'Toole. "

Lewis, meanwhile, the winner of the Kraft Nabisco Championship earlier this year, has yet to win since, although she has a pair of runner-up finishes. It's the first time Lewis has ever led after one round of play.

She'll have a tough time claiming her second career win, however, as she's faced with the task of fending off Tseng, a nine-time LPGA Tour winner, among others.

A host of talented players trail the two stars, including Jin Young Pak, Karen Stupples and Taylor Leon, all of whom shot a four-under 67 on the first day at Pinnacle Country Club.

Pettersen headlines a group of nine players that sit two strokes back at minus-three. Among the nine are Morgan Pressel, Paula Creamer and Na Yeon Choi; each are ranked among the top 15 in the world.

Tseng, who has four victories just this year, didn't start quickly, but got going with consecutive birdies on the par-five seventh and par-four eighth.

She maintained her score of two-under until the 14th, where Tseng hit her approach to three feet en route to the third birdie of her round.

"I feel very comfortable, confident. After that hole I was hitting my shot straighter," Tseng said. "I kind of work on my swing a little bit. And my caddie kept telling me, your swing's good, don't think too much, so that helps a lot, too."

On the 18th, still at three-under, Tseng used a 19-degree hybrid on her second to get to six feet. She made the ensuing left-to-right putt to notch her seventh eagle of the year and get to five-under.

Lewis, like Tseng, started slowly and finished strong.

She didn't get into red figures until a birdie at the par-three sixth, and her next birdie didn't come until the 10th. Lewis was still at only two-under with four holes left, but birdied three of the remaining holes to gain a share of the lead.

"I was so nervous on the first tee," Lewis said. "You want to play well, and I think early on I was kind of forcing things, just really wanting to play well and kind of forcing putts to go in, and I just had to stay patient and relaxed. The two birdies I made on 17 and 18, it was just unbelievable."

Near the bottom of the leaderboard was Michelle Wie, who had a round to forget. She managed only one birdie on the day to go with six bogeys and a double-bogey in a round of seven-over 78.

Meanwhile, two-time amateur champion Danielle Kang made her professional debut and began at two-under before slipping to three-over 74.

NOTES: Tseng's seven eagles are third on the LPGA Tour this season...Pernilla Lindberg recorded a hole-in-one on the par-three 11th and shot a two-under 69 on the day.