At the finish tonight, it was the champion who lost his poise. Wilfred Benitez dared to taunt Sugar Ray Leonard with a big confident grin at the outset of the 15th round, he dared later in the round to slug it out, and paid for it with the loss of his title, in the last six seconds.

Leonard was tiring badly, missing badly, and looking as though he had been pushed into the WBC Welterweight championship bout too soon, as his tenous lead hung in balance, in the champion's best round, the 14th, which Benitez won on all three judges cards.

A fan shouted above the rising din, "You don't look like the Sugar Ray I knew."

Somehow, Leonard found a burst power in his left hook, finally wiped the smile off Benitez's face, and then knocked him helpless with a hook, followed by a right cross, in a neutral corner.

The champion from Puerto Rico rose to his feet and feebly tried to hold off the windmill punches of a newly aroused Leonard but he was pretty much defenseless, blood gushing from a head wound, and in danger of being seriously injured.

Though a champion usually is allowed to finish with so little time in the last round, referee Carlos Padilla waved Leonard away and stopped the bout with 2 minutes and 54 seconds gone.

There were some protests about the abrupt ending, but Leonard had been ahead on all the officials' cards through 14 rounds.

Only the judges vote in Nevada. Art Lurie scored it 137-130, Harry Gibbs 136-134, and Ray Solis 137-133.

Leonard put down Benitez in the third round for a two-count with a classically executed straight left hand.

In the 11th round, the challenger staggered the champion with a sizzling left hook and two overhand rights to the head, the second of which knocked the mouthpiece from between Benitez's teeth.

It was unbeaten Leonard's 26th victory and his 17th knockout as he stitched the professional title to the Olympic championship he won in 1976 in Montreal.

Benitez suffered a cut at the hairline from an accidental butt in the sixth round and blood dripped until it obscured his vision. He appeared to suffer an injury to his left wrist in the next round and carried it limp at his side for a while, as if it were useless to him.

Later, he used that hand effectively. He said afterward that neither the butt nor the hand injury were to blame for his loss. He said the Leonard simply was the "better fighter" tonight.

"This is the greatest moment of my life -- it's even greater than Montreal," said Leonard.

He called it the toughest fight of his career, and said he went into the bout cautiously, not believing his 3 1/2-1 favorite status.

"I felt I had the edge going into the final round," he said. "But you can never really be sure how a fight is being scored."

Asked if he felt the referee was correct in stopping the fight with six seconds left, Leonard smiled and replied, "I thought it was pretty good of him.

"I said long ago I'd be the champion of the world even when people were saying I was just a Hollywood actor. But now I've taken the title back to Washington, D.C."

Benitez lost the first of 39 bouts, a draw being the only other blot on his record as the championship was lifted from his home town of San Just and deposited in Palmer Park, Md., the hometown of Wilmington, N.C., native Leonard.

It was a bout that was something less than spectacular in the early going, with both probing and feinting from almost flat-footed stances, despite their reputations for speed of hand and foot.

Not until the 14th round, when Leonard appeared to be a bit weary, had a swelling under his left eye, was missing wildly, and seeming unable to crash Benitez's defensive posture, was there much dancing. And then the champion appeared to be doing it to mock Leonard.

In the 13th, Leonard had been missing the elusive Benitez in the manner of an amateur, with swings and slaps, and the champion, for the second straight round, jolted the challenger with glove blows that belied his record of having scored only 23 knockouts in 38 previous fights.

Came the 14th and Leonard had lost the zip of the nifty swiftie who had stylishly polished off 16 previous opponents in 25 bouts. There was no steam in the forced shoeshine combinations or in the right hand chops he led with in his temporary frustration.

A massive left hook to Leonard's chin raised the prior persistent question, could he take a hard punch.

That was why Benitez flashed a taunting, confident grin, while awaiting the touching of gloves for the start of the final round. Leonard removed that with a stinging left, but absorbed a harder one in exchange. The action picked up when the challenger uncorked a smashing straight right to the jaw. Each scored with two single punches and then the challenger's long-muffled gloves exploded.

Three straight left hooks increased the redness around the champion's eyes and nose and Leonard began teeing off with bunches of punches in a dizzying rhythm. A shattering right was countered by Benitez's last menacing shot -- a left hook to the face.

As the champion desperately clawed, blinked, and scuffled for the temporary safety of a clinch, Leonard unloaded in a tight little arc a clubbing left hook that dumped Benitez on the canvas. A follow-up right was unneccessary, a consequence of Leonard's regained sharp reflexes.

Benitez, who had gotten up after three knockdowns and decisioned Bruce Curry, clambered to his feet in a manner befitting a champion. Then it was that Leonard, 23, finally silenced the critics, who had been skeptical of his right to be in a championship bout after having encountered so few quality opponents on a prudently arranged program.

In the other title bout here tonight, Vito Antuofermo retained his undisputed middleweight crown in a bloody 15-round draw with Marvin Hagler.

"My corner told me at the end of the seventh round that I was behind on points," said Antuofermo, a 4-1 underdog. "I knew I had to pick up the pace and I carried the fight to Hagler. I felt I deserved the decision but I'm satisfied with the draw because I am still the champion."

Promoter Bob Arum said after the bout that there would be a rematch in February.