American Lilly King edged Russia's Yulia Efimova to win the women's 100-meter breaststroke Monday in one of the most anticipated finals in the Rio Olympics.
A day earlier, in their preliminary heat, King pointedly disparaged Efimova after the event over her drug history.
The source of the feud is the suspension handed down to Efimova, who missed 16 months for doping and tested positive this year for the now-banned substance meldonium. The positive meldonium test was placed on hold while world anti-doping officials conduct further studies on the drug.
A smattering of boos greeted Efimova after she won her preliminary heat Sunday.
"If that's what she feels she needs to be able to compete, whatever, that's her deal," King told reporters after the prelim. "I'm here to compete clean for the U.S., and that's what I'm going to do."
King's time of 1:04.93 broke the Olympic record of 1:05.17 set by Australia's Leisel Jones at the 2008 Beijing Olympics. Efimova finished in 1:05.50, and American Katie Meili claimed the bronze (1:05.69).
In other women's swimming action, Hungary's Katinka Hosszu won the 100-meter backstroke, adding to her world-record victory in the 400 individual medley.
Hosszu didn't set a world record in the back, but her time of 58.45 seconds was good enough for a second gold.
Kathleen Baker of the United States settled for the silver in 58.75, and Canada's Kylie masse and China's Yuanhui Fu tied for the bronze in 58.76.
Hosszu, whose "Iron Lady" nickname comes from her grueling schedule, sat up on the lane rope and made a heart sign in the direction of her coach and husband, Shane Tusup.
In the women's 200-meter freestyle, Missy Franklin, one of the United States' top swimming stars at the 2012 Olympics, endured another stunning disappointment, failing to even make the final.
Franklin finished last in her semifinal heat with only the 13th-fastest time among 16 swimmers.
"I gave it everything I had but it just wasn't there," a tear-filled Franklin told reporters shortly after the race. "I just need to keep my head up and keep doing everything everything I can to be the best I can be."
Franklin touched in 1 minute, 57.56 seconds, which was actually slower than her time in the afternoon preliminaries.
As a bubbly, 17-year-old high schooler, Franklin won four golds and a bronze at the London Games. But she's endured a mystifying loss of form since turning pro last summer, struggling just to qualify for two individual events and a relay at the U.S. trials.
In 2012, Franklin competed in seven Olympic events. Now, all she's got left is the 200 backstroke and a likely spot on the 4x200 free relay team.
Information from The Associated Press was used in this report.