Michael Phelps delivered a blistering 200m butterfly time of 1 minute 55.32 seconds on Saturday, clocking the fastest time in the world this year to win the event at US Swimming's Columbus Grand Prix in Columbus, Ohio.
Phelps improved on Joseph Roebuck's 1:55.94 set at Britain's Olympic trials at London's Olympic Aquatics Centre on Tuesday.
Phelps sliced more than half a second off that time, gaining a comfortable victory over Tom Kremer (1:58.34) and Dakota Hodgson (1:59.31).
Japan's Kosuke Kitajima won the men's 200m breaststroke in 2:10.35, good enough for fourth on this year's world list.
Masayuki Kishida grabbed another victory for Japan, winning the men's 50m freestyle in 22.62 ahead of South African Graeme Moore (22.75) and Hungary's Krisztian Takacs (22.78).
Hungary's Zsuzsanna Jakabos cruised to victory in the women's 200m fly in a time of 2:08.09, which put her sixth in the world this year.
Natalie Coughlin won the women's 100m backstroke in 1:00.81, with Mexico's Maria Gonzalez Ramirez second in 1:00.96.
David Plummer's winning time of 53.73 in the men's 100m back put him fifth in the world his year. Matt Grevers was second in 53.79 and Brazil's Guilherme Guido third in 56.20.
Phelps, whose 14 Olympic gold medals include an unprecedented eight in one Games at Beijing in 2008, had plenty of energy left over to sign autographs for eager swim fans.
He said it's all part of his long-time goal of raising the profile of swimming in the United States.
"It's awesome that if you would have had this meet eight years ago you wouldn't have had half this many people here," Phelps said.
"There are a ton of people who are out here supporting us. That's something that is amazing."
Much of that is due to Phelps, who could boost interest even more with more gold medal-winning exploits in London later this year.
Phelps recently completed three weeks of altitude training in Colorado.
After what he admits were a lacklustre couple of seasons after Beijing, Phelps said he has plenty of room for improvement before London.
"We haven't done too much work in finishing the 200 fly," he said. "We're just trying to sort of get my stroke back and I think we finally found that.
"Now it's time to sort of fine-tune some things."
