Aaron Peirsol and Leisel Jones set world records to win their second gold medals at the world championships in Montreal on Friday, while Michael Phelps collected his fourth courtesy of another American relay victory.

American Peirsol lowered his own 200 metres backstroke record to join Australians Ian Thorpe and Grant Hackett as the only swimmers to win the same event at three world championships.

Jones slashed 0.72 seconds off Amanda Beard's world record to win the 200m breaststroke final, giving the Australian a second gold after her win in the 100m earlier this week.

Australia's Olympic champion Jodie Henry also won her second title this week with victory in the 100m freestyle to confirm her status as the fastest woman in the world.

Brendan Hansen, Peirsol's training partner, completed the 100m-200m breaststroke double for the first time by winning the longer race to extend the US lead at the top of the medal standings.

Phelps put the icing on the cake when he teamed up with Ryan Lochte, Peter Vanderkaay and Klete Keller to win the 4x200m freestyle relay in a combined time of seven minutes 06.58 seconds to take the gold ahead of Canada [Images] and Australia.

"This one is for Team USA," Phelps said. "This one is the most pleasing of them all."

Peirsol led all the way to take the gold in 1:54.66, 0.08 under the previous mark of 1:54.74 which he set at last year's US Olympic trials at Long Beach, California.

Markus Rogan of Austria finished second in 1:56.63 while American Ryan Lochte was third in 1:57.00 but all the plaudits were with Peirsol.

The 22-year-old Californian won the 100m earlier in the week and is unbeaten over 200m in five years, racking up a host of world and Olympic titles in that time.

"I'm starting to feel pretty possessive [about the 200m]," Peirsol said. "I feel like I've got a good grip on it in the sense I know how I need to swim it feeling good, bad or in-between.

"I think every time I get reminded that very few people have done something I feel pretty honoured. I know no-one has done what I've done in this race so far and I think I sort of keep that in mind."

Jones stopped the clock at 2:21.72 to erase the mark Beard set at Long Beach last year. Germany's [Images] Anne Poleska finished second and Austria's Mirna Jukic third.

Jones first took the record from Beard last year but it lasted just two days before the American snatched it back.

"Good things come to those who wait and I'm glad the way things have happened," said Jones, who lost her 100m record to Jessica Hardy this week but beat the American teenager in the gold medal race a day later.

"I think it has taken a lot of pressure off me and I think that if things don't work out for me in the future I'll still be happy because I've achieved my goals."

Henry stormed home on the last lap after being third at the turn to take out the premier women's event in 54.18, well outside the world record of 53.52 she set in Athens but still enough for her to add the world title to her Olympic crown.

American Natalie Coughlin and Malia Metella of France [Images] dead-heated for second place in 54.74.

"I'm trying to learn to deal with pressure," Henry said. "But I don't feel it yet [because] I haven't really had to deal with it."

Hansen failed to break his own world record when he weakened at the end after being under record pace for the first 150m, but had enough up is sleeve to take the title in 2:09.85 ahead of Canada's Mike Brown and Japan's [Images] Genki Imamura.

"We had a team meeting and we decided ... that we were all going to chase world records," Hansen said.

"I chased it pretty hard tonight and although I didn't quiet get there I'll still take the win."

Phelps laid the foundations for the American relay win with a slick opening leg to claim his fourth gold of the championships following his wins in the 4x100m freestyle relay, the individual 200m freestyle and 200m medley.

He has entered eight events but bombed out in the heats of the 400m freestyle and finished seventh in the 100m freestyle. He still has a chance to match Thorpe's championship record of six golds if he wins the 100m butterfly and the medley relay over the weekend.