J.B. Williams of Danville, Ky., shot a 7-under 65 on Tuesday to take the first-round lead in the Junior PGA Championship, and defending champion Ariya Jutanugarn of Thailand had a 66 to top the girls' division.
The 17-year-old Williams had eight birdies and a bogey at Sycamore Hills to match the competitive course record.
"It was a career day," said Williams, the Kentucky Junior PGA Championship winner. "I got hot on the front nine and kept it going on the back."
Early thunderstorms forced a two-hour delay.
"The rain delay this morning was a big factor," Williams said. "The greens were firm during the practice round, but today most of the guys were able to shoot at the pins and there were lots of low scores."
The 16-year-old Jutanugarn birdied the final three holes to match the course record she set last year in her 10-stroke victory.
"On the front nine I did not play so well," Jutanugarn said. "My driver was bad at the start. ... I got lucky on 16 when I chipped in and 17 is my favorite hole and I know I can make birdie there. Then I hit it to one foot on 18."
She finished with seven birdies and a bogey.
Jim Liu of Smithtown, N.Y., and Cameron Champ of Sacramento, Calif., were tied for second in the boys' competition at 67.
"I got off to a really hot start," said Liu, 2010 U.S. Junior Amateur winner. "The back was harder, but I was able to hold it together and close with birdies on 17 and 18."
Beau Hossler, the 17-year-old Mission Viejo, Calif., player who tied for 29th in the U.S. Open in June, matched Tyler McDaniel of Manchester, Ky., with a 68.
"I was pretty flawless today, minus the bogey at 18," Hossler said. "If I can keep the ball in the fairway, I will be right there at the end of the week."
Jutanugarn had a one-stroke lead over 15-year-old Samantha Wagner of Windermere, Fla.
"I was really happy with how I played today," Wagner said. "I was disappointed with how I played last year, but I love this course and knew I could play better."
Megan Khang of Rockland, Mass., shot a 68, and Jutanugarn's older sister, Moriya, had a 69.