Michael Phelps captured his third gold medal at the world championships in Montreal on Thursday to join Ian Thorpe and Grant Hackett as the only swimmers to win six individual world titles.
The American added another page to his glowing resume when he fought off a sustained challenge from Hungarian Laszlo Cseh to retain the 200 metres individual medley title he won in Barcelona two years ago, just an hour after he bombed out in the 100m freestyle final won by Italian Filippo Magnini.
Magnini pulled off a major upset to take the gold in a time of 48.12 seconds, making him the second fastest man in history behind world record holder Pieter van den Hoogenband.
Just a few minutes later, Otylia Jedrzejczak of Poland broke her own world record to win the women's 200m butterfly final after a thrilling duel with Australia's Jessicah Schipper that saw both women go under the old mark.
Australia did strike one gold when Giaan Rooney won the women's 50m backstroke final but the United States kept their lead on the medals table through Phelps and the women's 4x200m freestyle relay team.
Phelps had needed to win Thursday's blue-riband sprint to keep alive his dream of breaking Thorpe's record of six gold medals at a single championship but could only manage seventh place as Magnini pinched the title with a perfectly-timed swim.
Magnini stormed home on the last lap after being fourth at the turn to flash pass the South African duo of Roland Schoeman and Ryk Neethling.
Schoeman had led at the halfway mark almost three quarters of a second under van den Hoogenband's world record pace but weakened to finish second in 48.28 while Neethling also faded to take third in 48.34.
Jedrzejczak saved her best for last in her epic battle with Schipper, sneaking past the Australian in the last two strokes to win the gold in 2:05.61, 0.17 under the previous world record, which the Olympic champion set at the 2002 European championships in Berlin.
Schipper, who won the 100m butterfly title earlier this week, finished in 2:05.65 while Japan's Yuko Nakanishi was a distant third in 2:09.40.
Rooney won the backstroke sprint in 28.63 to add to the 200m freestyle gold she won at the 2001world championships in Fukuoka, Japan.
Gao Chang of China finished second in 28.69 while Antje Buschschulte was third in 28.72. Her German team mate Janine Pietsch finished sixth, just two months after she set the world record at 28.19.
Phelps had been aiming for a record eight gold medals in Montreal but struck out in his very first event when he failed to qualify for the 400mfinal on the opening day of competition.
He rebounded to win a relay gold then the 200m freestyle but his failure in the 100m ended his chances of winning at least seven, bettering Thorpe's haul of six golds from Fukuoka and equalling Mark Spitz's tally from the 1972Munich Olympics.
Despite having to back up just an hour after the 100m,Phelps was determined not to dwell on his defeat as he climbed onto the blocks for the medley final.
There was a hint of a boilover when Phelps trailed for the first 100mafter Cseh went through the butterfly and backstroke legs under world record pace, but the American was in front when they switched from breaststroke to freestyle for the last lap.
Phelps pulled away to win in 1:56.68, three quarters of a second outside his own world record, with Cseh second in 1:57.61 and American Ryan Lochte third in 1:57.79.
Natalie Coughlin, Katie Hoff, Whitney Myers and Kaitlin Sandeno combined to win the 4x200m relay in 7:53.70after a titanic battle with Australia.
Libby Lenton had given the Australians a big lead when she completed the first leg in 1:57.06, a second and half faster than Solenne Figues's winning time in the individual 200mfinal.
The Australians were still in front after 700m but Linda MacKenzie could not hold off Sandeno in the last 100m and had to settle for second in 7:54.06 with China third in 7:57.29.