England's Charley Hull shot a flawless round of 63 on Thursday to take a one-shot lead into the second round of the Ford Championship in Arizona.
Starting on the back nine, Hull picked up four shots before the turn and birdied five holes down the stretch to head into the clubhouse with her nose in front on nine under par.
She leads by one from Denmark’s Nanna Madsen, whose only blemish on the day was a bogey on the par-four fifth hole.
Amanda Doherty, Taiwan's Peiyun Chien, Japan's Minami Katsu and Canada's Brooke M. Henderson are tied for third at seven under, with four South Koreans in the form of Ina Yoon, Jin Hee Im, Mi Hyang Lee and Sei Young Kim.
Defending champion and world number one Nelly Korda sits on five under, leaving her tied for 17th place.
Ireland's Leona Maguire is in a share of 59th place after carding a 70 to trail Hull by seven shots.
After her round, the overall leader told reporters: "I kind of tweaked my driver at the beginning of the week and I really, really, really hit it well today.
"I felt like that put me in a lot of good positions. I putted pretty well. I chipped pretty well. I hit it pretty well with my iron shots. I don't think I missed a green and didn't really miss any fairways.
"I was hitting it good and felt confident. Just felt good out there."
