South Korea's Chun In-Gee fired a four-under 68 to maintain a share of the lead at the halfway stage of the LPGA Tour's Portland Classic on Friday.
Chun has a two-round total of 10-under 134 which leaves her in a three-way tie with 19-year-old Canadian Brooke Henderson, who shot a five-under 67, and veteran American Stacy Lewis who had a bogey-free 64.
Those three are two shots ahead of the rest of the field, with Jodi Ewart Shadoff of England (67), Ai Miyazato of Japan (67) and Moriya Jutanugarn of Thailand (69) tied for fourth at eight under.
Chun's 68 followed a 66 on Thursday as she seeks her first win of 2017 after four runner-up finishes.
"I really like this course. Also the spectators are so kind here," said Chun, who has six top three results on the year.
Two-time defending champion Henderson shot her second-straight 67 on Friday and had the lead outright at 11-under thanks to an eagle on the 11th. But a bogey five holes later dropped her into a tie at 10-under with the other two.
"I feel like I have a solid game plan," she said. "Any time I'm in double digits after two days I'm really happy. I will just try and continue that trend over the next two days."
Lewis, of Toledo, Ohio, carded eight birdies and no bogeys in her round, which she considered one of her best of the year.
"My swing felt a lot better," Lewis said. "I found something after the round yesterday. Felt like any hole I could make birdie on."
Lewis said earlier if she wins should would donate all her prize money to the Hurricane Harvey flood victims in Texas.
Sitting at seven-under are Kim Kaufman, Taiwan's Candie Kung (69) and Nasa Hataoka of Japan (70). Kaufman moved up from a tie for 73rd after the first round by shooting a 65 on Friday.
Miyazato is retiring at the end of the season and this is her last official LPGA Tour event on American soil.
"I'm glad I made the decision," she said. "I was kind struggling to make the decision last few years. Even though after I announced my retirement I've been really happy. I've been really positive about my game and trying to enjoy it as much as I can out there."