Sugar Ray Leonard won the WBC welterweight title with a fifteenth-round knockout of Wilfred Benítez in 1979. He lost it to Roberto Durán by a close decision in June 1980 and regained it five months later in the infamous No Más Fight, in which Duran quit in the eighth round. In June 1981, Leonard moved up to the light-middleweight division for one fight, knocking out Ayub Kalule in nine rounds to win the WBA light-middleweight title.

Hearns won the WBA welterweight title in 1980, scoring a second-round knockout of Jose 'Pipino' Cuevas in Detroit, Michigan. He made three successful title defenses, stopping Luis Primera, Randy Shields, and Pablo Baez.

Promoted as "The Showdown" Leonard (30-1 with 21 KO) fought Hearns (32-0 with 30 KO) on September 16, 1981 at Caesar’s Palace in Las Vegas, NV to unify the world welterweight championship in a scheduled fifteen-rounder. They fought before a live crowd of 23,618 and a worldwide TV audience of some 300 million.