Ryan Lochte saw off rival Michael Phelps to claim first place in the 400-metre individual medley at the United States Olympic trials.
Both men booked their places at London 2012, but it was Lochte who came away with the psychological advantage as he finished first in a time of four minutes 7.06 seconds.
Phelps came in just behind him in 4mins 07.89secs, while Tyler Clary, who led the race at one point, completed the top three in 4:09.92.
Today was the first of a possible six finals in which the two men could clash this week, with the 100m and 200m freestyle, 200m backstroke, 200m medley and 100m butterfly also on the agenda.
Phelps won gold in the 400m medley in 2004 and 2008, but afterwards stated his intention to ditch the event.
He has now gone back on that promise, although Lochte has had the edge over his rival of late.
Elsewhere, Peter Vanderkaay and Conor Dwyer sealed their places on the team in the 400m freestyle, while Elizabeth Beisel and Caitlin Leverenz were first and second in the women's 400m medley.