Tyson held the WBA, WBC and IBF belts, while Spinks held the Ring Magazine belt and was considered the lineal champion.
Held at the Atlantic City Convention Hall in Atlantic City, New Jersey and promoted as "once and for all", it was the richest fight in boxing history to that point, grossing some $70 million.
Michael Spinks had been world light-heavyweight champion from 1981-85, going undefeated in the division and making 10 successful title defences. In 1985 he moved up to heavyweight and challenged long-reigning IBF and Ring champion Larry Holmes, winning by a close decision. In doing so Spinks became the first reigning light-heavyweight champion to win the heavyweight title. Spinks defeated Holmes again in a rematch and then successfully defended his title against Steffen Tangstad and Gerry Cooney. He was stripped of his IBF belt for not facing Tony Tucker but as he held the lineal title and remained undefeated, some continued to recognise him as the true heavyweight champion.
Mike Tyson turned professional in 1985 and won his first 19 fights by knockout, quickly garnering media attention and establishing an "aura of invincibility". In November 1986 Tyson knocked out Trevor Berbick to win the WBC heavyweight title; at 20 years old, Tyson was the youngest heavyweight champion in history. He followed up by beating WBA champion James 'Bonecrusher' Smith and IBF champion Tony Tucker to unify all three major belts. He also knocked out three other former world champions: Pinklon Thomas, Tony Tubbs and Larry Holmes. By 1988 Tyson had become "the most talked about - and marketable - heavyweight champion since Muhammad Ali".
Tyson attacked Spinks from the opening bell, landing a solid left hook in the first ten seconds and forcing Spinks to cover up. Spinks clinched and was driven back to the ropes by another Tyson attack. He moved off the ropes but Tyson trapped him again; a left uppercut and a right hand to the body forced Spinks to take a knee after a minute, the first time Spinks had been knocked down in his professional career. Spinks took a count of four before rising. As the two men moved towards each other Tyson turned away from a Spinks right hand and responded with a left-right combination to the head which put Spinks down again. This time he was unable to rise and referee Frank Cappuccino counted him out.
The fight was over after 91 seconds.
1988 Ring Magazine Round of the Year.
This was the fight in which Tyson, three days short of his 22nd birthday, produced what is widely regarded as the most dominant performance of his career. Many experts agree that Tyson would have been a match for any heavyweight in history on this night.
Spinks was less than a month from his 32nd birthday and had campaigned the vast majority of his professional career as a light heavyweight.
Spinks, who didn't hold a belt but was regarded as the lineal champion after twice beating Larry Holmes, had a perfect 31-0 record. Tyson had won 34 bouts in a row, with 30 KOs, including seven world title wins in 16 months.
The fight, at the Convention Hall in Atlantic City, New Jersey, attracted enormous worldwide interest and was billed "Once and For All", meaning the winner would be recognized as the undisputed heavyweight champion (even though Tyson met the criteria for being an undisputed champion already, he won all three titles [WBC, WBA, IBF], Spinks was the linear champion of the division).