LAS VEGAS, AUG. 1 -- Mike Tyson did few of the things he was expected to tonight, save for becoming the undisputed heavyweight champion of the world.

International Boxing Federation titlist Tony Tucker gave up the third and final belt to the 21-year-old WBC and WBA champion, but not without going the scheduled 12 rounds at the Las Vegas Hilton Convention Center before Tyson won a unanimous decision.

In doing so, Tyson became the first fighter since Leon Spinks defeated Muhammad Ali in 1978 to hold a unified heavyweight title. But the victory lacked glamor and it lacked verve, for the young slugger displayed none of his renowned knockout ability, and in the audience was the opponent that he still has to beat before he is acknowledged as truly undisputed: Michael Spinks.

As the fight wore on, there was growing appreciation from a crowd of 7,419 for Tucker (35-1, 30 knockouts), the obscure IBF champion who became only the fourth opponent to take Tyson (31-0, 27) the distance. But while Tucker eluded Tyson for much of the evening, he scored rarely. Tyson dominated it, as judges awarded the fight by scores of 119-111, 118-113, and 116-112. All in all it was an uneventful bout that was saved only by its historical significance.

"I'm undisputed heavyweight champion of the world, that says enough," Tyson said.

But Tyson added that he made a major miscalculation in taking Tucker lightly. He wasn't alone; the 28-year-old was as much as a 15-to-1 underdog, and was not expected to last more than five rounds. Instead, he staggered Tyson with a devastating left uppercut within the first 30 seconds of the opening round, won the third round on two cards and the 10th round outright, according to the three judges. He eluded Tyson with good mobility and glimpses of an accomplished jab. Had he displayed any offense, it would have been an intriguing bout.

"I didn't throw enough punches," Tucker said. "I still thought I outboxed him. But I have to go along with the judges."

Tyson said: "I took him a little for granted, and that was a big mistake.

"He put up a good fight. He's been around seven years, he's experienced, and no one expected it to go this far."

Only Mitch Green, James Tillis and Bonecrusher Smith were able to take Tyson the distance. In each case, they did it by clinching, running and occasionally jabbing. Tucker's strategy was exactly the same. But Tyson helped him by throwing few combinations; his punches were all of the knockout variety, and many of them missed. It was clearly not his finest night, and had Tucker displayed any more weapons, it might have been much closer.

But Tucker said he hurt his right hand about a week before the fight, which troubled him from the second round on. Tyson said he stopped punching around the sixth or seventh, and floated through the remainder of the fight with only the brief flurry at the end.

"He punched it out, he was a game fighter," Tyson said. "But he stopped fighting in the seventh round. I think he knew then he couldn't win. He was hoping for a miracle. There's none here."

Tucker's first punch was a startling one. It came out of nowhere, as Tyson was making his usual bull-like charge, and was a half-loop that caught him in the side of the head. Tyson, who does not normally feel pain during a fight, felt that one.

"When I fight I don't think about the pain," Tyson said. "But he hit me with a good shot. He picked me right up in the air."

Tucker began his Ali-like waving and circling in the seventh, but that was the sum of his activity until the 10th. Then he skipped away and once more scored with jabs as Tyson missed repeatedy. Tucker waved again in the 12th, and Tyson obliged him by charging, but was continually unable to do the damage he wanted to, and Tucker counterpunched in earnest.

"When someone gets it in their mind they're going to survive, there's nothing you can do to knock them out," Tyson said.

It was not a marvelous fight, but nor was it horrid. Anyway, the 18-month $22 million HBO series to unify the title had already lost its glamor long before when Spinks was stripped of his IBF belt for refusing to fight Tucker. With Spinks lurking in a bleacher seat tonight still unbeaten at 31-0, it indeed seemed presumptuous to call Tyson the undisputed champ.

The so-called unification was made downright silly, if not hilarious, by promoter Don King's strenuous efforts to publicize it. He planned a postfight coronation, with the winner to be presented with a chinchilla cape, a jeweled sceptor, and a crown studded with what he called "fabulous doo-dads."

Spinks took the opportunity to steal some thunder from the bout by holding his own press conference earlier in the day at the nearby Riviera Hotel. There, promoter Butch Lewis jokingly draped a pink towel around Spinks' shoulders, and set a cardboard crown on his head. Then, Spinks said what he thought of the fight.

"It's like something you get sent in the mail," he said. "It's a paper title."

Shot back Tyson later, "I'm undisputed champion of the world. I'll fight any man." But he added of Spinks, "He's not really on our agenda."