Nelly Korda reeled off six successive birdies to hit the front at the Women's PGA Championship after the second round.
Korda was red-hot at Atlanta Athletic Club in Georgia, where the American golfer used a birdie binge to claim a one-stroke lead on Friday.
A five-time LPGA Tour champion, Korda had consecutive birdies from the fourth to the ninth hole as she tied the Women's PGA Championship 18-hole scoring record.
"I don't know, I guess I just blacked out, out there," Korda said afterwards as she became only the third professional to card a 63 at Atlanta Athletic Club, joining Steve Stricker and Mark O'Meara.
Korda – eyeing her maiden major title – is 11 under through 36 holes, a shot better off than Lizette Salas (67).
Salas, who was the overnight leader, posted consecutive 67s to remain bogey-free heading into the weekend.
Three-time PGA Championship winner Inbee Park (68) is six shots off the pace in a tie for seventh, while defending champion Kim Sei-young (69) bounced back from a forgettable 76 to avoid the cut.