Hansen defended his world championship in the 100-meter breaststroke Monday night, touching first in 59.80 seconds, with Kitajima of Japan right behind in 59.96. Brenton Rickard of Australia earned the bronze.

Michael Phelps was back in the pool for his first individual event, easily advancing to the 200-meter freestyle final Tuesday night.

But the American was second quickest behind leading qualifier Pieter van den Hoogenband of the Netherlands.

Hoogie was under Ian Thorpe's world-record pace through 100 meters before falling off and finishing in 1 minute, 46.33 seconds. Phelps' time was 1:46.75 in the other semifinal.

''I think I can go a bit harder in the final, so we will see tomorrow if it's good enough,'' Van den Hoogenband said.

Phelps downplayed the chance of a world record in the final.

''Anything is possible. But Thorpe swam the record in nearly perfect fashion,'' he said. ''There are a couple of guys who want to beat it tomorrow. It would make a dream come true for me, but if it's there, it's there. If not, then not.''

Phelps and Van den Hoogenband were part of the ''Race of the Century'' at the 2004 Athens Olympics, with Hoogie finishing second and Phelps third behind gold medalist Thorpe. Any hopes of a full-fledged rematch ended when Thorpe retired a few months ago.

Phelps opened his bid for eight gold medals Sunday when he led off the United States' victorious 400 freestyle relay.

After two days of swimming, the United States and Australia were tied with six medals each. The Americans had three golds to the Aussies' two.

In the breaststroke, Hansen hit the wall and turned around to check the scoreboard. Seeing his finish, he pumped his left fist and signaled No. 1 with his left index finger.

''I'm not very pleased with the time, but it's been shown in the past that you don't break world records when you're in a battle like that,'' Hansen said. ''I couldn't see him. I didn't know where he was, but I knew he was there.''

It was virtually a two-man race between Hansen, the world record holder, and Kitajima, who swept the breaststroke events at the 2004 Athens Olympics. The American was bitterly disappointed to finish second in the 100 and third in the 200 at those games.

The gold medal Hansen really wants will be up for grabs next year at the Olympics. That's when he hopes to dethrone Kitajima on swimming's biggest stage.

''It's just motivation for the Olympics,'' Hansen said. ''That's where the big races are.''

Hansen has carried a chip since Athens and it surfaced again Monday night, when he noted his latest win didn't stop reporters from bringing up his losses three years ago.

''It doesn't make up for you guys. You still call him Olympic champion and me just a guy who's got a bunch of medals,'' Hansen said. ''I obviously won't make it to your par until I make an Olympic medal.''

He's already on his way, with four consecutive victories over Kitajima.

He beat the Japanese star in the 100 at the world championships two years ago in Montreal. Hansen won the 100 and 200 over Kitajima at the Pan Pacific championships in August before claiming victory in Melbourne.

''Last year I was really struggling. This year has started quite well,'' Kitajima said through a translator. ''Hansen is a very, very strong swimmer. I knew if he did his best time today, I would not be able to compete with him. I was only one stroke behind him, so I am quite happy.''

Hansen and Kitajima were the only swimmers to break 1 minute in the final that was contested before plenty of empty seats at Rod Laver Arena.

''Sometime if there was synchro swimming (for men), me and him should team up,'' Hansen said. ''It's just one of those things where he brings out the best in me and I bring out the best in him. If the crowd loves it and puts more attention on our sport, so be it.''

The two rivals don't speak each other's languages, so they communicated with a post-race handshake.

''That was my way of showing respect and congratulating him,'' Kitajima said.

Libby Lenton and Jess Schipper gave Australia a 1-2 finish in the women's 100 butterfly final. Lenton's time of 57.15 broke Schipper's meet record of 57.23 set two years ago in Montreal.

Schipper settled for silver in 57.24.

American Natalie Coughlin earned the bronze in 57.34. Her teammate Rachel Komisarz was fifth.

Lenton clearly enjoyed her surprising victory. She pumped her left arm, shook her head in amazement and then slapped the water. During a victory walk around the pool, Lenton bopped her head to the Men at Work hit ''Land Down Under.''

American teenager Katie Hoff won her second consecutive world title in the 200 individual medley. Hoff, teammate Whitney Myers and Shayne Reese were all under world-record pace at different points in the race, but Hoff couldn't hang on to beat the 10-year-old mark.

Hoff finished in 2:10.13, lowering her meet record from two years ago.

''I definitely felt pressure,'' she said. ''Just trying to think, 'Post a time.' Obviously, I was shooting to get under 10. But at these kind of meets, just race for the win and the time will take care of itself.''

Kirsty Coventry of Zimbabwe took the silver, her same result in 2005. Stephanie Rice of Australia earned the bronze. Myers finished fourth.

Roland Schoeman of South Africa defended his title in the men's 50 butterfly — a non-Olympic event. He won in 23.18 seconds.

''I struggled a little bit trying to fight the water,'' he said. ''I wanted to crush it like a big diamond.''