ST. LOUIS (AP) - Mark McGwire's 500th home run ball has been sold to a sports memorabilia collector.

The agent selling the baseball, Michael Barnes, said Wednesday the buyer is a ``well-known collector who firmly believes that this ball is one of the most valuable ever hit.'' Barnes didn't reveal the price.

McGwire hit his 500th homer on Aug. 5 in a 10-3 loss to the San Diego Padres.

McGwire made it to 500 in 5,487 at-bats, breaking Babe Ruth's record of 5,801. Jim Shearer, a 28-year-old St. Louis architect, survived a mad scramble at Busch Stadium to retrieve the ball.

Barnes, president of One-of-a-Kind Auctions in Festus, offered $100,000 before last season to any fan catching McGwire's 500th. The $100,000, however, was just an advance on what the ball might bring at an auction.

After hitting his 500th home run, McGwire said the bat he used to hit it would be donated to the Hall of Fame. He had hoped to see the ball join it. McGwire has said he believes the items are historical and should not be sold.

Last season, Barnes helped Phil Ozersky, a 26-year-old researcher at Washington University, sell the 70th home-run ball from McGwire's record season in 1998. Canadian comic book tycoon Todd McFarlane paid $3,005,000 for it.