Denis Pankratov eclipsed his own world record in the 100-meter butterfly final on Wednesday to complete a golden double.
The black-capped Russian swam more than half the first length of the 50-meter Georgia Tech pool below the surface and hit the turn in 24.19 seconds, well inside world-record pace.
Australia's Scott Miller, the fastest qualifier from the morning's heats, staged a magnificent challenge on the return length but could not catch Pankratov.
Pankratov won in 52.27 seconds, 0.05 of a second inside the world mark he set at the European championships in Vienna last August, to complete a butterfly title double after winning the 200 event on Monday.
Miller claimed the silver in 52.53 and Vladislav Kulikov took the bronze in 53.13.
"He was just too good," Miller said of his Russian conqueror. "Twenty meters out he seemed to find something that I didn't think he had."
Rozsa grabs 200 breaststroke gold
World champion Norbert Rozsa, silver medalist at the 1992 Barcelona Games, finally won gold when he led a Hungarian one-two in the men's 200-meter breaststroke.
Rozsa, who failed to make the final of Saturday's 100 breaststroke, made dramatic amends when he and fellow Hungarian Karoly Guttler overtook Russian pace-setter Andrei Korneyev on the final length for gold and silver.
European champion Korneyev took the race out fast and for the first 100 meters was inside the world-record schedule American Mike Barrowman set at the 1992 Olympics.
But he could not keep the Hungarians at bay and Rozsa, double silver medallist in Barcelona, just prevailed in the final thrust for gold, touching in 2:12.57.
Guttler was bronze medalist behind Rozsa in the 200 at the 1994 worlds.