In the end, one of the greatest heavyweights in boxing history quit because he didn't want to get off his stool and fight anymore. Two-time heavyweight champion Mike Tyson lost to an unknown Irishman last night at MCI Center when referee Joe Cortez stopped the fight before the seventh round at the urging of Tyson's corner.

Tyson, once the most feared boxer in the world after winning his first 37 bouts, said he would retire after losing for the third time in four fights. It was a bizarre ending to the career of one of the most electric and confounding athletes of the past generation.

As he left the ring, Tyson was booed by many in the crowd of 15,732 for quitting, and one fan threw a cup of soda at him as he left the arena. Tyson responded by using his middle finger to express an obscenity.

"I can't do this anymore," Tyson said. "I can't do this to myself and I'm not going to embarrass the sport I love. This is just my ending. That's it. It's finished."

Quitting against a fighter such as Kevin McBride will further tarnish whatever is left of Tyson's once-proud legacy, but his reputation would have been even further damaged had the fight been stopped in the sixth round.

Late in that round, after Tyson was unable to knock down McBride with a flurry of punches, he first tried to break his opponent's left arm and then purposely head-butted him, opening a cut below McBride's left eye.

"He tried to break my arm a couple of times," McBride said. "I think he tried to bite me."

When Tyson locked up McBride's left arm in a corner of the ring, Cortez separated the fighters and McBride shook his arm in pain. Later in the round, Tyson purposely head-butted McBride in front of his opponent's corner. Cortez stopped the fight while McBride's trainers tried to stop the bleeding, and Cortez deducted two points from Tyson for the intentional foul.

"I was desperate," Tyson said. "I wanted to win, man."

McBride is fortunate that Tyson decided to quit. Despite out-classing Tyson in five of the six rounds, two judges, Tammye Jenkins and Stephen Rados, somehow had Tyson leading, 57-55, when the fight was stopped. Judge Paul Artisse had McBride winning by the same score.

Tyson was unable to hurt McBride, who was 38 pounds heavier at 271, and McBride's quick jabs seemed to hurt Tyson as he tired.

McBride's trainer, Goody Petronelli, said of Tyson: "His equilibrium was shot. He was trying to get up and he couldn't. If he had, he would have really gotten hurt."

Tyson (50-6, 44 knockouts) seemed to be in trouble near the end of the sixth round, after McBride (33-4-1, 28 KOs) hit him with a hard, right-handed overhead punch and left uppercut. With less than 10 seconds left in the round, McBride pushed down Tyson, nearly entangling him in the ropes.

Cortez ruled the fall a push and not a knockdown, but Tyson couldn't get up off the canvas. Cortez seemed to plead with Tyson to get up and after about eight seconds, Tyson slowly walked back to his corner.

"I didn't want to get up," Tyson said. "I was tired."

Less than a minute later, after Tyson's trainer, Jeff Fenech, asked Cortez to stop the fight, the referee walked to McBride's corner and raised the Irish heavyweight champion's right arm, declaring him the winner. Tyson sat dazed in his corner, his attempt at a comeback and financial solvency seemingly over for good.

"I'm not going to let my friend get hurt," Fenech said. "It was enough."

Tyson, who turned a $400 million fortune into $34 million of debt, still owes creditors more than $20 million after declaring for bankruptcy three years ago. He will receive about $2 million from the $5.5 million purse for fighting McBride, according to Monica Turner, his former wife. Tyson owes the Internal Revenue Service more than $15 million and Turner more than $6.6 million in unpaid child support and alimony.

"When I get some money, I'll pay them," Tyson said. "If I don't have any money, I won't. That's just the way it is."

Tyson, who will turn 39 on June 30, was fighting for the first time since he was knocked out in the fourth round by Englishman Danny Williams on July 30. That loss was considered the worst of Tyson's career, but McBride was even more lightly regarded.

McBride, 32, was paid only $150,000 to fight Tyson and wasn't expected to last longer than a couple of rounds. He was even hypnotized before the fight to bolster his confidence.

"I didn't think a real warrior would quit on his stool like that," McBride said.

Mike Tyson slumps against the ropes at the end of the 6th round and doesn't come out for the 7th, even though he was leading on two of the three judge's scorecards. Kevin McBride wraps himself in the Irish flag: "I proved everyone wrong tonight."Mike Tyson battles Kevin McBride; the ex-champ also head-butted McBride for a two-point penalty. "I was desperate," Tyson said. "I wanted to win, man." Tyson (50-6) has lost 3 of his last 4 fights.