Brittany Lincicome had six birdies in a 6-under 65 to take a one-shot lead from Hyo-Joo Kim of South Korea at the halfway stage of the Evian Championship on Friday.
The 28-year-old American has won a major before, the Kraft Nabisco in 2009, but clinched the last of her five LPGA titles in 2011 at the Canadian Women's Open.
She finished second behind South Korea's Inbee Park at this year's LPGA Championship, when she also led after 36 holes.
The day after making history with the lowest ever score in a women's or men's major with a 10-under 61, Kim had four bogeys and rescued her round with three birdies on the back nine — including a 35-footer on the last hole.
Countrywoman Mi-Jung Hur is three shots behind Lincicome.