Stephen Fahy set a new senior national record of 57.20 seconds in the 100 metres butterfly heats at the World Championships in Perth, Australia, yesterday.

And that was good enough to qualify him yet again for the Commonwealth Games to be held later this year in Malaysia.

Earlier this week at the Worlds, Fahy and Stephen Troake both qualified for the Games in the 100 metres freestyle, and on Thursday Troake set a new national record in the 100m backstroke.

Fahy continued the trend yesterday. Undaunted by the unseasonal conditions, he enjoyed a flying start in the 100 butterfly and touched the wall at the end of the first lap in a fast 27.16. He came home in 30.04 to place second in his heat, although it wasn't enough to qualify for the final.

But the effort shaved almost five-tenths of a second off Fahy's old record of 57.65 set last year at the CCCAN meet in Cuba and easily meets the Commonwealth Games qualification time of 57.84.

Fahy, however, wasn't altogether happy with his performance as, in his opinion, he finished with a short stroke as he touched the wall to complete his swim.

He badly wanted to go under 57 seconds and with the knowledge that he can improve his finishing approach, he hopes to achieve that at the next opportunity.

Today will mark the last time in the Perth pool for both Fahy and Troake as Troake competes in the 50 metres freestyle and Fahy takes to the water in his other favourite event, the 200 metres individual medley.

Troake will be out to better the Commonwealth Games qualifying standard of 24.90 while Fahy hopes to lower his senior national record of 2:09.77, also set in Cuba last year. The Games qualifying time for this event is 2:13.90.

Meanwhile, in other action yesterday, Jenny Thompson won her fourth gold medal while the much maligned Chinese women finished one-two in the 200-metre individual medley.

Thompson, the meet's biggest winner, swam the butterfly leg as the United States took the women's 400 medley relay in four minutes, 1.93 seconds, just outside China's world record.

Kurt Grote won the men's 200 breaststroke, giving the Americans a total of nine golds for the championships.

Thompson, who has two events remaining, won the 100 freestyle and butterfly golds and was a member of the winning 400 freestyle relay team. In the medley relay, she teamed with Lea Maurer, Kristy Kowal, and Amy Van Dyken.

Grote came into the meet ranked first in both the 200 and 100. Despite that lofty ranking, Grote said he was surprised to be in the thick of a battle with France's Jean-Christophe Sarnin, who had led for much of the race, and Olympic champion Norbert Rozsa of Hungary.

"I'm a little bewildered,'' Grote said. "I saw people all around me and thought I was in the mix. I didn't realise I had a chance to win, but obviously I did enough to win and now I feel great.'' Grote finished in 2:13.40. Sarnin was second in 2:13.42 and Rozsa another .17 seconds behind.

In the women's 200 individual medley, world record-holder Wu Yanyan finished first and Chen Yan second. US-based Martina Moravcova of Slovakia was third.

Wu finished in a meet-record 2:10.88. Chen followed in 2:13.66 and Moravcova was third in 2:14.26.

Wu's victory was China's third gold medal, after they won 12 of 16 events four years ago in Rome. Chen won the 400 medley and 400 freestyle titles.

Earlier this week, four Chinese swimmers, including three women, were suspended after testing positive for drugs. And last week, one female swimmer and a coach were disqualified from the championships after Australian Customs found 13 vials of muscle-building human growth hormone, a banned substance, in Yuan's bag.

Australia's Michael Klim won his third gold, coming within a tenth of a second of his world record in the 100-metre butterfly, finishing in 52.25.