Michael Phelps made a great start to his bid for a record eight Olympic gold medals when he qualified fastest for Saturday's 400 metres individual medley final.

The Athens Games also began well for Australian Ian Thorpe who easily qualified for the 400 freestyle final.

American teenager Phelps cruised through his opening heat in four minutes 13.29 seconds, almost five seconds off the world record he set at the United States trials last month, but still well clear of his nearest rivals.

"I'm just glad to finally be here," Phelps said.

"I felt comfortable and in control today. I'm not worried about the time, I just want to get my hand on the wall first."

Hungary's Laszio Cseh qualified second fastest in 4:14.26 with Italian Alessio Boggiatto third in 4:15.78 but both were well behind Phelps, who slowed down noticeably in the final leg to conserve his energy.

There was no repeat of the embarrassing false start that almost cost Thorpe the chance to defend his 400 freestyle title as he easily qualified for the eight-lap event.

Thorpe was disqualified at the Australian trials when he tumbled off the blocks before the gun had sounded and was allowed to swim the event in Athens only after his team mate Craig Stevens surrendered his spot.

The 21-year-old Thorpe made a cautious start, taking almost a second before he left the blocks, and won his heat in 3:46.55 to qualify second fastest for Saturday's final.

Thorpe's time was more than six seconds outside his world record but the Australian was unshaven and swam well within himself.

"I was trying to make sure I was last off the blocks this morning so I won't be last tonight," said Thorpe.

Australia's Grant Hackett, runner-up to Thorpe at the past three world championships, posted the fastest qualifying time when he stopped the clock at 3:46.36 while improving American Larsen Jensen was third ahead of Italy's 200 medley champion Massimiliano Rosolino.