BEIJING - As Mark Spitz's record of seven golds in one Games came closer to falling, world records continued to tumble.

Michael Phelps began his day by resetting his own world record in the 200-meter butterfly, the race he has dominated more thoroughly than any other in his career, with a time of 1:52.03.

It not only put Phelps halfway to the eight gold-medal mark that the world so eagerly anticipates him reaching, but it made him the most golden Olympic athlete of all time.

The 10th gold medal in his career broke a tie Phelps held with four other athletes, including Spitz and American track legend Carl Lewis. It also tied him with fellow American swimmer Jenny Thompson for the most medals, 12, for any Olympian.

Phelps' world record was the fourth set of Wednesday morning's session (Tuesday night in the States). It was also just the fourth race.

The world record frenzy, which no doubt will draw a critical eye by the time these Games are complete, began in the first semifinal of the men's 100-meter freestyle.

Frenchman Alain Bernard, who held the record heading into the Games but lost it when Australia's Eamon Sullivan swam a blistering opening leg of the 400 free relay, regained his record when he touched the wall at 47.20 seconds.

That record lasted all of about two minutes, as Sullivan hit the pool to drop .15 seconds off that time. Sullivan's 47.05 drew gasps from the audience, and was perhaps the most impressive of the record-setting session.

"It's a high-level competition, so it's normal," Bernard said of Sullivan breaking his record once again. "The most important is the final."

The two Americans who helped Phelps earn his second goal in the 400 free relay, Jason Lezak and Garret Weber-Gale, struggled some in semis, with Weber-Gale not even qualifying for the final.

Lezak, whose 46.06-second anchor leg of the relay has become the swim of the meet, finished third in his semifinal in a time of 47.98. That's .40 seconds behind his personal best. In the next race, Weber-Gale was fifth in a time of 48.12, which is .34 seconds behind his best time.

Both sprinters acknowledged Tuesday that they were a bit drained after the emotional and physically taxing gold-medal effort in the 400 relay, and it appeared to affect them in this event. Weber-Gale still has the 50 free left to race, while Lezak will likely anchor the U.S. men's 400 individual medley relay.

When the men's semifinals were through, the records continued to drop, this time in the women's 200 free.

American Katie Hoff, who qualified second for the event and was swimming out of lane five, swam an American record of 1:55.78.

And that was still only good enough for fourth, as Italian Federica Pellegrini set the world record with a time of 1:54.82. Pellegrini had set the world record two days earlier in a preliminary race, and the top three finishers in the final were all under the that previous world record mark.

Hoff continues to be one of the most heart-wrenching stories on the American side. It was four years ago, as a 15-year-old, that Hoff failed to qualify for the final in the 400 IM despite entering the Athens Games holding the best time in the world.

Immediately after the race, shaking from nerves and fatigue, Hoff vomited on the side of the pool.

Earlier in these Games, Hoff had her best chance at individual gold in the 400 free. She led the race by nearly a body length through the first 350 meters. But she faded down the stretch as Rebecca Adlington barely reached the wall first. Hoff settled for silver. She also collected a bronze in the 400 IM.

Then came Phelps, who knew he had one more race ahead of him, the 800 free relay, before entering the pool for the 200 fly.

He was behind after the first 50 meters, being pushed by New Zealand's Moss Burmester in lane one.

But Phelps quickly caught and past Burmester, then coasted to his fourth world record in his fourth final.

"I couldn't see anything for the last 100, my goggles were pretty much filled up with water," Phelps said. "But it's fine. I wanted to break the record. I wanted to go 1:51 or better, but for the circumstances, I guess it's not too bad."