Defending champion Lexi Thompson posted a bogey-free 5-under-par 66 on Saturday, but In Gee Chun did her one better with a 65 and the two were tied for the lead heading to the final round of the Meijer LPGA Classic at Blythefield Country Club in Grand Rapids, Mich.
Thompson, shaking off back problems that have bothered her this week, birdied five of the first 13 holes but missed a few chances coming home to finish at 15-under 198 for 54 holes.
"I just hit a lot of drivers, and if my game's on it comes together," said Thompson, who is the only American player to win on the LPGA Tour this season. "It's just a nice setting and atmosphere. It's one of our best tournaments."
"I got a lot of work done (on her back) last night. It was hurting quite a bit, but I have it all taped up and it helped out out there today, and I took my pain pills. It was better today than yesterday."
Chun, who also played bogey-free, caught Thompson when she made four birdies in a five-hole stretch through No. 15.
"Today my iron shot great," said Chun, who will defend her U.S. Women's Open title next month. "I liked my putting very well. I was so good at rolling the ball on the line. We had a lot of spectators here. I was so happy for them to see my play. I make great round today.
" ... I'm always excited to play in the last group so I'm ready. I enjoy it. ... I play with Lexi. It's very exciting."
Sei Young Kim of South Korea, the 2015 LPGA Rookie of the Year after winning three times, made an eagle on the 11th hole en route to a 65 and was one stroke back in solo third. She was followed by Carlota Ciganda of Spain, who was another shot behind after a 66, and Shanshan Feng of China, who is three down in fifth following a bogey-free 65.
Top-ranked Lydia Ko of New Zealand birdied four holes in a row through No. 13 on her way to a 67 and was four shots back in a tie for sixth with Xi Yu Lin of China, who also had a 67.
Amy Yang of South Korea and Amelia Lewis both carded 69s and were another shot behind in a tie for eighth with So Yeon Ryu of South Korea, who came in at 70.
Brooke Henderson of Canada, who won the KMPG Women's PGA Championship last week in a playoff over Ko and rose to No. 2 in the world, shot 72 and was tied for 21st.