Spaniard Azahara Munoz put in an almost flawless round at the ANA Inspiration at the Mission Hills Country Club in California but has to share the lead at the end of the first round.
Munoz carded a five-under 67 after producing a bogey on the final hole, meaning she has to share the lead with Japan's Ai Miyazato, after an otherwise superb back nine at the year's first major.
She was just two under after the front nine, notching birdies on the first and fifth holes, before birdies on the 10th and 11th put Munoz in a strong position.
She added further birdies on the 15th and 17th holes with a bogey on the 18th the only downside to her day.
World number one Lydia Ko is three shots off the pace in equal 14th as one of 10 players on two under.
Ko was one under after her front nine, but bogeys on the 10th and 13th holes - both followed by birdies - put her on the back foot with just an 18th-hole birdie keeping her in touching distance of Munoz.
Park Inbee, a 17-time LPGA Tour winner, joins Ko on two under after back-to-back bogeys on the 15th and 16th holes.
Ahead of them, Catriona Matthew, Shiho Oyama and Lee-Anne Pace are tied in third on four under.
Jang Ha-na, winner of two LPGA Tour events, is one of eight on three under and tied for sixth place.