Brooke Henderson set the pace in the opening round of the Women's PGA Championship, but she has a new challenger in Lee Mi-rim after Friday's second round.
Henderson had two bogeys on each of the front and back nines for a second-round 73 and a share of the one-stroke lead at the Sahalee Country Club in Sammamish, Washington.
The 18-year-old Canadian started brightly with a birdie on the third hole, but back-to-back bogeys on the next two seemed to dent her confidence.
She had another bogey on the 10th before a birdie on the 17th, but a dropped shot on the final hole saw her miss out on the chance to take the outright lead into the third round.
Lee, however, started the day tied for 10th but birdies on the first, third and sixth holes saw the South Korean finish level at two under at the halfway mark of the tournament.
The pair hold a one-stroke lead over world number one Lydia Ko (70), Brittany Lincicome (70) and Gerina Piller (69) - who are the only five players under par.
I.K Kim - who was tied for second overnight - shot two over on a difficult day, while Christina Kim (74) dropped from equal second to a tie for 11th.
Meanwhile, two bogeys and a double-bogey saw three-time defending champion Park Inbee (79) miss the cut at nine over the card.