Chella Choi fired six birdies in a five-under par 67 on Friday to seize a one-stroke lead over fellow South Korean Shin Jiyai and American Morgan Pressel in the LPGA Championship.
After steady rain washed out play on Thursday, delaying the start of the second women's major of the season, Choi was quick to get into the swim on Friday morning with five birdies on the front nine at Locust Hill Country Club.
She added another birdie at the par-four 10th before her only bogey at 13 on a day when she hit all 14 fairways in regulation.
Her accuracy was especially important on the rain-soaked course, where the wet weather only made the rough more punishing.
"I hit a really good driver today," Choi said. "I hit 14 fairways. So I'm really happy. My goal is just keep in the fairway, so I'm really happy."
Choi, seeking a first LPGA title, was able to limit her mistakes, even though she played much of her round in rainy weather.
Shin played without a bogey, grabbing three of her four birdies on Locust Hill's back nine.
Pressel countered three bogeys with seven birdies, unleashing four straight birdies from the 15th to cap her round and grab her share of second place.
"I played pretty well out there," Pressel said. "I didn't put myself in any really bad trouble, which you can certainly find on this golf course."
American Brittany Lincicome was alone in fourth on 69, while South Korean Pak Se-Ri and American Jessica Korda were a further stroke back on two-under 70.
Taiwan's Tseng Ya-ni had a hole-in-one for eagle at the par-three 15th and was among a group of nine players on 71, while world number one Park In-Bee of South Korea headed a big group at even-par 72.
"After I hit it, I knew it was a good shot. But I was just trying to get good distance and I wasn't thinking it was going to go in hole," Tseng said of her ace.
Park's round ended on a low note with a double-bogey six at the par-four 18th, where she said poor club selection was to blame.
"I was hitting the ball great today," she said. "I didn't putt as well as I thought I would have, but I putted really bad last week and it was getting better this week, so that's a positive to take. I played very good until the last hole."
Park said her victory in the Kraft Nabisco Championship, the first major of the year, gave her added incentive to do well in the second. She didn't think par was a bad way to start the week.
"I'll take even par every day here," she said. "It's not a bad start."
She has three more rounds to gain ground, but Sunday promises to be a demanding day. After losing a day of play on Thursday, organizers hope to play the second round on Saturday and both the third and fourth rounds on Sunday.