After four years of preparation, and his evolution from a gangly teenaged athlete to the most renowned swimmer of his generation, Michael Phelps became the first member of the 2004 U.S. Olympic swimming team on Wednesday, shattering a world record in the process, and taking another historic step toward the Games next month in Athens.

The 19-year-old, 6-foot-4 swimmer from Baltimore County electrified the crowd at the U.S. Olympic trials, streaking to victory in the evening final of the 400-meter individual medley in a time of 4 minutes 8.41 seconds, more than a half-second better than his old record of 4:09.09.

It was the fourth time in two years that Phelps has broken the world record in the event. It was also the first of six events in which he is entered at the trials.

Phelps, who lives with his mother in Rodgers Forge, Md., near Towson, is shooting to win seven gold medals in Athens, matching the 1972 feat of Mark Spitz at the Munich Games.

Sporting a new, short haircut, and wearing a gray and blue, knee-length suit, Phelps wore his headphones until just before the start, with Eminem's "Till I Collapse" pounding in his ears.

He led the race from the start, galloping through the butterfly leg of the race and closing in on a world record pace during the backstroke. Fueled by growing excitement of the crowd chanting "Go! Go!" with each stroke, he zoomed through the breaststroke and freestyle, finishing several lengths ahead of second-place finisher Erik Vendt, 23, of North Easton, Mass.

"He was so far ahead I don't think I pushed him at all," Vendt said.

"When the crowd's behind you, you can definitely tell something's going on," Phelps said immediately after the race. "I heard it coming off the wall from back to breaststroke, from there on I just tried to feed off the crowd."

U.S. Olympic men's team coach Eddie Reese, of the University of Texas, joked: "We'll have to review the tape to see if that's good enough to make the team," quickly adding, "That was awesome. That was a good way to start the meet. . . . We knew he was going to be good, and we want him to be real good."

Phelps's coach at the North Baltimore Aquatic Club, Bob Bowman, said: "I think he wanted to come out and have a good swim and know that we were sort of on the right track. There's a long way to go and there are a lot of races with a lot of good people in them. This is one. How many -- 15 more to go? I try not to count."

Phelps is scheduled to swim 17 times before the trials end next week.

The 400 individual medley is one of three events in which the powerful and versatile Phelps holds the world record.

It was the second time Phelps has made the Olympic team. He did so in 2000, at age 15, becoming the youngest male U.S. Olympian since 1932. He swam the 200-meter butterfly in Sydney, but finished fifth.

Then, he was green and dazzled, he said, "a little kid coming up in the swimming world," showing up for one race without his bathing suit tied.

Now he weighs about 200 pounds and is as lean and muscular as a panther.

"I'm very happy with how I swam tonight," Phelps said during a post-race news conference, sporting an Orioles baseball cap and munching a food bar. "Going into a race it's always a goal of mine to do a best time and swim as fast as I can. I'm extremely satisfied and looking forward to that race at the Olympics."

He said it was a relief to make the Olympic team. "The Olympic trials is probably more stressful than the Olympic Games itself so being able to come in and get the first race under your belt, [you can] step back and relax a little bit."

His victory Wednesday came before a large crowd perched in makeshift bleachers erected around a temporary pool outside the Long Beach Convention Center, within sight of the orange-and-black smokestacks of the mothballed oceanliner Queen Mary and with the smell of the ocean in the air.

Last July Phelps set the world record of 4:09.09 in the 400 IM, more than a second faster than the world record he had set in the event just the previous April, which was 0.37 second faster than the one he had set nine months before that.

Such stunning time reductions in so short a period have people here talking about Phelps one day breaking the four-minute barrier.

"A lot of people are kind of joking when they talk about it," said Tarrah Smith Pollaro, media coordinator for USA Swimming, the sport's U.S. governing body. "The fact that people are even talking about it is pretty significant. Even that it's in the realm of possibilities talks about how good he is."

Phelps is so young that he could easily compete in two more Olympiads after Athens, lowering his times all the while.

On Thursday Phelps is scheduled to compete in his second test, the 200-meter freestyle, an event in which he holds the American record of 1:45.99. The world record of 1:44.06 is held by Australia's Ian Thorpe.

On Friday he is set to swim both the 200-meter butterfly, in which he holds the world record of 1:53.93, and, most likely, the final of the 200 freestyle.

Michael Phelps gets U.S. Olympic trials off to flying start by winning the 400-meter individual medley and in the process earning a spot on team. Michael Phelps catches his breath during the butterfly portion of his record-setting 400 individual medley.Stroke for stroke Phelps proved to be way ahead of the field, whether it be the backstroke, top left, breaststroke, top right, or freestyle, below.