Phelps smashed his own standard in the 400-meter individual medley by 2.04 seconds, becoming the most successful swimmer ever at the worlds.

The 21-year-old American joined countryman Mark Spitz as the only swimmers ever to win that many golds at a major international meet. Of course, Spitz' achievement came on the sport's grandest stage -- the Olympics.

Phelps hopes to equal the feat or go one better at next year's Beijing Games.

A Polish swimmer staged the biggest upset of last night in the grueling 1,500 freestyle, where Aussie Grant Hackett's run of four consecutive titles ended.

Mateusz Sawrymowicz won the gold medal in 14 minutes, 45.94 seconds against the fastest field in history.

Yury Prilukov of Russia took the silver. David Davies of Britain earned the bronze.

Hackett struggled home seventh, ending a disappointing meet for the soon-to-be-married world record holder. He earned a bronze in the 400 free and was seventh in the 800 free.

American Larsen Jensen was fourth, and teammate Erik Vendt eighth.

Katie Hoff looked like a chip off Phelps' block in winning the women's 400 IM. The 18-year-old out of the same North Baltimore club that launched Phelps set a world record of 4:32.89.

Hoff won by an even bigger margin than Phelps -- 7.25 seconds ahead of Yana Martynova of Russia. Stephanie Rice of Australia settled for bronze.

Just like Phelps, Hoff won the race on the breaststroke portion, when she dipped under world-record pace and opened a huge lead.

Phelps and Hoff accounted for the night's only world records. American swimmers set 11 of the meet's 14 marks.

Phelps never got a chance at an eighth gold in Melbourne after his U.S. teammates were shockingly disqualified in the 400 medley relay preliminaries this morning.

Ian Crocker, who had been in position to derail Phelps in the 100 fly before losing to his rival, dove in too early on an exchange, causing the DQ.

Without the heavily favored United States in the medley relay, it was a wide-open race that had the screaming crowd on its feet throughout. Australians Matt Welsh, Brenton Rickard, Andrew Lauterstein and Eamon Sullivan outtouched Japan by 0.23 seconds for the gold. Russia finished third.

Phelps was gracious in his first public comments about Crocker's gaffe.

''When Team USA comes into a swim meet, we come as a team and we exit as a team,'' he said. ''There are things that don't happen exactly as we want it to, but it's better to happen now than next year.''

Still, Phelps closed out his eight-day run in style, winning the 400 IM in 4:06.22 -- easily improving his old standard of 4:08.26 set at the 2004 Athens Olympics.

Ryan Lochte took the silver -- a whopping 3.52 seconds behind his teammate -- for his fifth medal of the meet. Luca Marin of Italy earned the bronze.

Phelps and Lochte dueled through much of the 400 IM. Phelps was under world-record pace after 150 meters of butterfly. Lochte narrowly took over the lead at 200 meters during the backstroke, his specialty.

But Phelps roared back on breaststroke, again dipping under record pace.

''That's probably my most improved stroke over the last six months to a year,'' he said.

He went 1.49 seconds lower on the first of his two freestyle laps before powering home with the red line that indicates the world-record pace lapping at his feet.

Phelps checked his time and leaned heavily on the lane rope, holding up his right index finger in the No. 1 sign.

''That was my last race, so I wanted to finish strong,'' he said.

Phelps' five world records equaled the number he broke at the 2003 worlds in Barcelona. Back then, he won six medals, including four gold.

As Phelps soaked in the applause during his victory stroll, Crocker looked on pensively from the stands, chewing gum.

Phelps stopped to hug his mother Debbie, who showered him with kisses and whispered in her only son's ear. Before leaving her, he handed over his bouquet.

Lochte couldn't resist breaking out his gold, silver and diamond-crusted grill for the victory walk, getting cheers and laughs from other swimmers when he flashed the metal mouth caps he wore earlier in the meet on a dare from his teammates.

Libby Lenton of Australia won her fifth gold medal, taking the women's 50 freestyle in 24.53 seconds. American Natalie Coughlin was last, closing out a five-medal showing, including two golds.

The evening opened with finals in two non-Olympic events -- the men's 50 backstroke and women's 50 breaststroke.