Mika Miyazato carded a 4-under 68 on Saturday to take a 2-shot lead after two rounds of the Safeway Classic.
Miyazato, who is going for her first LPGA Tour title, finished 36 holes at 11- under-par 133.
Last week's winner, So Yeon Ryu, also shot 68 to move into second place at minus-9. Cristie Kerr and Inbee Park both carded 2-under 70s in round two and share third place at 8-under-par 136 at Pumpkin Ridge Golf Club.
Sydnee Michaels, who shared the first-round lead with Miyazato, managed an even-par 72 and fell into a tie for fifth at minus-7. She was joined there by Paula Creamer (69) and women's world No. 1 Yani Tseng (67).
Tseng, who won three times in a 4-event span earlier this year, posted back- to-back under par rounds for the first time since the Kraft Nabisco Championship.
"It's been a long time. I haven't shot like 5-under for a couple months. It feels great," said Tseng, who last shot 67 in the first round of the Kia Classic in March. "My game seems like it's coming back, and I'm hitting so many good shots just like before."
Miyazato played the back nine first on Saturday and carded her first birdie on the par-3 11th. She parred the other eight holes on her opening nine.
On the front side, Miyazato made a steady move up the leaderboard. She birdied the par-3 third to move to minus-9.
Miyazato was in the lead after a birdie on the par-4 sixth. Two holes later, she posted the final birdie of her round to move to 11-under. She parred the last to cap a bogey-free round.
"I played so good today, because I had bogey-free round," Miyazato said. "My second shots were very good. I had so much frustration with my putting on the [first] nine, but I made three birdies on the back nine."
Ryu, last year's U.S. Women's Open winner, flew out of the gate with three birdies in a row from the 10th. She also birdied the 15th and 18th to make the turn at 10-under.
After three straight pars, Ryu stumbled to a bogey on the par-5 fourth. She ran off five consecutive pars to close out her round.
"I think it's really hard to keep focusing on my golf after my winning," Ryu admitted. "The front nine I shot 5-under, but unfortunately the back nine I made one bogey, and I missed a lot of birdie putts. So today I finished at 4- under. I think my problem is I just missed a couple of utility shots."
NOTES: The cut line fell at 3-over-par 147 with 76 players advancing to the final round...Among those that missed the cut were Hee Kyung Seo, Ryann O'Toole, Morgan Pressel and Lexi Thompson...Park has posted six straight top-10 finishes.