In the first event of the evening, Phelps (Baltimore, Md.) broke the hallowed world record in the 200m freestyle, finishing in 1:43.86 and shattering Ian Thorpe’s old mark of 1:44.06, set July 25, 2001. Phelps led the entire race, finishing ahead of silver medalist Pieter van den Hoogenband (Netherlands) by more than two seconds. Korea’s Tae Hwan Park was the bronze medalist in 1:46.73. The record was Phelps’ second in less than 40 days. He broke his own world record in the 200m butterfly on February 17.

The gold medal was the second of the meet for Phelps, who also won as a member of the U.S. 400m freestyle relay on Sunday.

Natalie Coughlin (Vallejo, Calif.) struck next – in the next race in fact – swimming the 100m backstroke in 59.44, which lowered her own five-year-old world mark of 59.58, set August 13, 2002. Coughlin got out to a convincing lead at the 50-meter mark, turning in 28.30. She finished four-tenths ahead of silver medalist Laure Manaudou of France and nearly a second ahead of the bronze medalist, Reiko Nakamura of Japan. Coughlin, who is swimming five events at this meet, is the reigning Olympic champion in the event.

Aaron Peirsol (Irvine, Calif.) completed the U.S. world record trio, posting a time of 52.98 in the 100m back to improve his own record of 53.17, set April 2, 2005. Peirsol took off to an early lead, clocking a time of 25.8 at the turn. Peirsol finished almost a half-second in front of teammate and silver medalist Ryan Lochte (Daytona Beach, Calif.) while Great Britain’s Liam Tancock took the bronze in 53.61. Peirsol, who has held the world record in this event since the Olympic Games in Athens (8/21/04), will swim his specialty, the 200m backstroke, on Friday.

Also breaking into the record books, Katie Hoff (Towson, Md.) took down a three-and-a-half year-old American record in the semi-finals of the 200m freestyle. Hoff’s time of 1:57.29 earned her the fourth seed in tomorrow’s finals. The record formerly belonged to Olympic gold medalist Lindsay (Benko) Mintenko. Also advancing for the USA is Dana Vollmer (Granbury, Texas), who claimed the eighth seed with a semi-final time of 1:58.71.

Other Team USA medalists tonight included Olympian Tara Kirk (Bremerton, Wash.) and distance specialist Kate Ziegler (Great Falls, Va.). Ziegler set a championship record in the 1500m freestyle, touching in 15:53.05. The 18-year-old had a two-second lead after the first 250 meters, and extended it to finish more than two seconds ahead of silver medalist Flavia Rigamonti of Switzerland. Ziegler started the race on world-record pace, but finished just a second shy of Janet Evans’ 19-year-old mark.

Kirk cruised to a second-place finish in the 100m breaststroke, with a time of 1:06.34. She finished just behind world record-holder Leisel Jones of Australia, who posted a championship-record time of 1:05.72. In third place was the Ukraine’s Anna Khlistunova, who out-touched U.S. swimmer Jessica Hardy (Long Beach, Calif.) by less than a second in 1:07.27. Hardy finished fourth in 1:07.38.

Team USA has won 11 medals in the first three days of the Championships.

Two American men advanced in semi-final heats tonight. Phelps returned to the pool for the semi-final in the 200m butterfly and finished in 1:55.13 to claim the top seed in Wednesday’s finals. Club Wolverine teammate Davis Tarwater (Knoxville, Tenn.) narrowly missed a spot in the finals, placing 10th in 1:56.58. Brendan Hansen (Havertown, Pa.), who won the gold medal in last night’s 100m breaststroke, took the top seed in the 50m breast with a time of 27.51.

Footage of the world and American record performances, as well as all the action from tonight’s finals, is available on-demand at wcsn.com. Finals set for tomorrow night include the men’s 200m butterfly, 50m breaststroke and 800m freestyle as well as the women’s 200m freestyle.