The heavyweight championship bout between Mike Tyson and Michael Spinks tonight matches fighters with opposing styles and attitudes vying for a common goal.

"I'm a fighter, I'm not a boxer," Tyson says."I'm a boxer, I'm not a fighter," Spinks says. "I don't even like the word fighter."

Tyson and Spinks will battle for the undisputed title in a bout scheduled for 12 rounds at the 21,500-seat Convention Center. The fight will be the richest heavyweight title bout in history.

Both are undefeated, and the winner becomes the first undisputed heavyweight champion since Leon Spinks in 1978.

As in the ring, the fighters have different styles when dealing with the countdown to the bout.

Tyson, a puncher, puts on a macho face before fights, and says the pressure of a big bout makes him perform better. Spinks, a more cautious boxer, admits feeling trepidation, but says that does not mean he is afraid of his younger and stronger opponent.

"I just want to get it on," says Tyson, a 7-2 favorite. "The threat of losing is exciting to me. I love the excitement of a challenge with my health and title on the line.

"It psyches me up. Anyone who threatens me with losing is in trouble." Spinks says he will show up to win.

"I'm nervous as a leaf on a tree but I'm going in anyway," Spinks says. "I've outgrown my days of being afraid of people. Most athletes are afraid of not performing well.

"But I've never run from anyone. I would hope my best performance is still in me. I think I have what it takes to win."

Spinks, who is 6-foot-2 1/2, weighed a career high 212 1/4 at Saturday's weigh-in. Tyson, 5-11, was 218 1/4.

Tyson, of Catskill, N.Y., and Spinks, of Greenville, Del., both have legitimate claims to the heavyweight title.

Tyson, 21, is 34-0 with 30 knockouts and owns the World Boxing Council, World Boxing Association and International Boxing Federation championships. Spinks, 31, is 31-0 with 21 knockouts and held the IBF title from 1985 until he was stripped last year for refusing to fight the No. 1 contender. He maintains he is still a champion because he never lost the title in the ring.

Tyson enters the fight after a troubled training camp, which was marred by marital and managerial problems. If he performs poorly, his relationships with wife Robin Givens and manager Bill Cayton will probably be blamed.

But Tyson said he can shut out all his personal problems when he steps in the ring. He said Cus D'Amato, Tyson's legal guardian and trainer for seven years before his 1985 death, taught him to focus on boxing.

"Ever since I was 13 I was groomed to be the heavyweight champion of the world," Tyson said. "I didn't go to school, I had tutors and everything was brought in to me. I was taught to handle the pressures.

"Why should I be afraid? He's the one who should be afraid. I'm the best fighter in the world."

Tyson and Spinks have already had careers of which to be proud. Tyson became the youngest heavyweight champion in history when he won the WBC crown at the age of 20. Spinks, a 1976 Olympic gold medal winner, stood as undisputed light heavyweight champion before moving up in weight to stun Larry Holmes in 1985. His decision victory over Holmes made him the first reigning 175-pound champ to win a heavyweight title, and is the basis for his claim as the true champion.

But Spinks' career is winding down - win or lose Monday - and he may be judged in history largely by his fight against Tyson.

"This is a test for me," he said. "I'll take my chances.

"I'm nervous as usual. But I'm not here just making a show. I come to fight. I'm not much of a talker, I never have been. I'll be there to do whatever I can to win."

Spinks' cautious attitude puzzles Tyson.

"In my camp we don't `try,' we do or we die," Tyson said. "And we're going to do.

"I'm not a predictor, but it won't go the distance. My objective is to knock him out in spectacular fashion."