Michael Phelps opened defense of his Olympic title in the 200-meter butterfly with the fifth-fastest qualifying time in the preliminaries on Monday.
Phelps has yet to have the quickest time in the morning heats at the London Games four years after he won a record eight gold medals in Beijing.
He finished third in his heat at 1 minute, 55.53 seconds, trailing Dinko Jukic of Austria and US teammate Tyler Clary to the wall.
Phelps' mother, Debbie, nodded her head slightly when she saw her son had safely advanced. He was the slowest qualifier for the 400 individual medley final on Saturday, and his surprising fourth-place finish kept him off the medals podium.
Jukic had the top time of 1:54.79, while Clary was second-best at 1:54.96 in advancing to the evening semi-finals.
Velimir Stjepanovic of Serbia was third at 1:54.99. Others who made the semis included Chad le Clos of South Africa (fourth), 2008 bronze medalist Takeshi Matsuda of Japan (eighth), 2008 silver medalist Laszlo Cseh of Hungary (ninth), Wu Peng of China (10th) and Nick D'Arcy of Australia (12th).
Federica Pellegrini qualified fastest in the 200 freestyle, keeping the Italian on course to defend her Olympic title.
Pellegrini touched in 1:57.16 in the third of five heats, with American teenager Missy Franklin swimming in the lane next to her. But the other American, Allison Schmitt, had the second-quickest time of 1:57.33 in advancing to the evening semifinals on the third day of swimming competition.
"It definitely feels like I'm ready to swim," Schmitt said.
"I've been preparing for this meet all year. It's been fun so far and I'm looking forward to having more fun tonight."
Franklin was third-best in 1:57.62. She led the first 150 meters before Pellegrini surged ahead over the final lap.
"I didn't expect to be that fast this morning," Franklin said.
"It's a stacked event. It's definitely going to be fun. I need to keep my energy up. It's going to be tough for sure."
Pellegrini is the world champion and world record-holder in the event. She finished fourth in the 400 free on Sunday.
"I'm happy with the time," Pellegrini said.
"The bitterness from last night ended right after the race. I know I gave my all."
Also moving on were Sarah Sjostrom of Sweden (tied for seventh), Australians Bronte Barratt (10th) and Kylie Palmer (11th), and 400 free gold medalist Camille Muffat of France (12th).
Muffat was tired after a fitful night of sleep.
"I kept getting up and opening the drawer the medal was in to check it was real and not a dream. It is so beautiful," she said. "This event and the relay is just a bonus for me now."
Photograph: Clive Rose / Getty Images