Brendan Hansen broke his own world 100m breaststroke record, Michael Phelps won the 400m individual medley and Katie Hoff set a US 200 individual medley record to open the US Swimming Championships on Tuesday.
Hansen won in 59.13 seconds to shatter the world record he set on July 8, 2004 at US Olympic qualifying in Long Beach for the Athens Games.
"I didn't think I'd come to nationals and break the 100," Hansen said. "I thought the 200 was more in sight."
"I just wanted the opportunity. Just give me a lane and give me the chance. It was just a matter of me putting all the little things together and just having a good race," he said.
Hansen completed the first 50m in 27.66 seconds and surged to the finish.
Scott Usher was a distant second in 1:01.07 with Matthew Lowe third in 1:01.02.
Phelps, the Athens Olympics hero who is aiming for more multi-medal stardom in two years at the Beijing Games, captured the 400 individual medley in 4:10.16, 1.9 seconds off the world record he set at Athens but 1.37 ahead of runner-up Ryan Lochte.
Phelps was ahead of world record pace at 200m, but fell behind at the breaststroke leg.
"That was a pretty disappointing swim," Phelps said.
"I feel like I should have gone faster, but that's how it goes. Ryan had a great swim. It's better than we were last year, but by no means is this where I want to be right now," he said.
Hoff won the 200 individual medley in 2:10.05 to break the American record of 2:10.41 she set last year at the world championships in Montreal and defeat runner-up Whitney Myers by 2.01 seconds.
The world record remains the property of China's Wu Yanyan, who set the mark of 2:09.72 in 1997 at Shanghai.
Klete Keller and Kate Ziegler won 400 freestyle titles. Keller's came in 3:44.27, .16 off his American record and 2.54 ahead of runner-up Peter Vanderkaay.
Ziegler won in 4:05.75 with Hoff second in 4:05.83.
"I was hoping for a little faster time," Keller said.
"I wanted to do a best time. That was my goal. I've got to work on going out fast and being able to bring it back that fast. I need two of those first 200s," he said.
Natalie Coughlin won the women's 100 butterfly in 57.78 seconds, edging Rachel Komisarz by one-hundredths of a second.
The meet serves as a qualifier for the US team that will compete at the Pan Pacific Championships later this month at Victoria, Canada.