Yana Klochkova held off a fierce challenge from Kaitlin Sandeno to defend her title in the women's Olympic 400m individual medley on Saturday.
Yana Klochkova just edged American challenger Kaitlin Sandeno
The Ukrainian clocked a time of four minutes 34.83 seconds to add to the gold she won in Sydney four years ago.
Klochkova was taken to the wire by American rival Sandeno, who finished 12 hundredths of a second behind in a dramatic final.
Georgina Bardach of Argentina came third in a time of 4:37.51 .
Klochkova's time was just outside the the world record of 4:33.59 she set in winning her first Olympic title in Sydney.
Hungarian Eva Risztov, runner-up at last year's world title, led the race after the opening butterfly leg but the 22-year-old
surged ahead after the backstroke.
She was still in front at the end of the breaststroke before Sandeno snuck past her turning for home
But Klochkova, who also won a 400 freestyle world title in 2001,
reeled her in to get to the wall first.
Klochkova is hoping to repeat the 200-400 medley double she completed in Sydney four years ago.
Katie Hoff of the United States, ranked number one in the world heading into the Olympics, failed to reach the final after
finishing 17th in the morning heats.