Judge Lloyd O Whitehead granted Phelps probation before judgment, meaning his record will be expunged if he follows the terms of probation. Phelps pleaded guilty to driving while impaired, and prosecutors dropped charges of driving under the influence, underage drinking and failure to stop at a stop sign.

"I recognise the seriousness of this mistake," Phelps told the judge in a packed courtroom.

"I've learned from this mistake and will continue learning from this mistake for the rest of my life."

The 19-year-old Phelps was fined $250, must attend a meeting sponsored by Mothers Against Drunk Driving, and must give speeches to students at three schools by June 1, advising them about making choices and warning them about the dangers of alcohol.

Whitehead also ordered Phelps to abstain from alcohol and illegal drugs during his probation.

As Phelps left the courthouse, the star who won eight medals at the Athens Olympics -- six gold -- was besieged by autograph seekers.

"The past few months have been extremely hard," Phelps said.

"I'm looking forward to getting back into the water and getting back to a normal routine."

Under the terms of his probation, Phelps must report to a probation supervisor once a month by telephone or as directed by the court.

"The reason for that is because of his travel," State's Attorney Davis Ruark said.

Normally a probationer would have to report in person.

Phelps, who grew up near Baltimore, recently moved to Michigan. He's scheduled to enroll in January at the University of Michigan, where his longtime coach Bob Bowman is the new men's swimming coach. As a professional, Phelps cannot compete for Michigan.

Whitehead agreed to go along with the terms of a probation agreement worked out between defense attorneys and the state.