Fina World Championships
Date: 17 July-2 August (swimming from 26 July) Venue: Rome
Live/highlights on BBC Two, Red Button and BBC Sport website
Replay - Phelps smashes own butterfly record
Michael Phelps recovered from defeat in the 200m freestyle with an emphatic win and new world record in the 200m butterfly at the World Championships.
The American romped home in one minute 51.51 seconds to take more than half a second off his own mark.
Italy's Federica Pellegrini set another world record to win gold as Jo Jackson finished fourth in the 200m freestyle.
Seven new world records on Wednesday took the total set at the Championships to 22 with four days still remaining.
Only 15 world records were broken at the last World Championships in Melbourne and Grant Hackett's 1500m freestyle mark is now the only one set by a swimmer not wearing a body suit.
The sport's governing body Fina have announced that restrictions on the material and fit of swimsuits will be introduced in 2010.
Poland's Pawel Korzeniowski and Japan's Takeshi Matsuda could not repeat the upset caused by Paul Biedermann on Tuesday as they finished second and third behind Phelps.
Britain's Michael Rock claimed a creditable seventh.
"I wanted to step on it in the first 100 metres to get out there in the clean water, and that's pretty much what happened," said Phelps.
"It was a lot more pain last night in the freestyle than tonight."
Pellegrini delighted the home crowd as she smashed the record she set in the semi-final to become the first women to dip under one minute 53 seconds as she clocked 1.52.98.
Olympic open-water silver-medallist David Davies finished fifth in the final of the 800m freestyle as China's Zhang Lin stretched the field with a superb performance.
Federica Pellegrini claimed gold in a world record time
The 22-year-old ratcheted up the pace at the 350m mark to come home in seven minutes 32.12 seconds and chop more than six seconds off Hackett's four-year-old world record.
Gemma Spofforth claimed a new British record but failed to qualify for the 50m backstroke final.
The 21-year-old finished sixth in her semi-final where Germany's Daniela Samulski improved on her own world record.
But the second semi-final saw Russia's Anastasia Zueva go one-hundredth of a second better to snatch the landmark away.
James Goddard posted a new British record as he won his individual medley semi-final in one minute 57.12 seconds, but team-mate James Roebuck finished seventh and outside qualification in his race.
Ellen Gandy failed to reproduce her best form in the first 200m butterfly semi-final finishing eighth in two minutes 8.55 seconds as Australia's Jessicah Schipper hunted down China's Liu Zige.
In the other semi-final Hungary's Katinka Hosszu claimed Gandy's European record as she edged out the United States's Mary Descenza over the final few metres.