The distance (boxing) 19, 1987. While the International Boxing Federation, which had recently broken away from the WBA, continued to hold onto the position there was no documented medical evidence to show a 15-round fight is more dangerous than a 12-round fight, they eventually voted to shorten their championship distance to 12 rounds as well on June 3, 1988. The last heavyweight 15-rounder title fight was on October 16, 1987 between Mike Tyson and Tyrell Biggs. The last middleweight 15-rounder title fight was a World Boxing Board title match on June 7, 1997 in which Jose Alfredo Flores won a split decision over
Heavyweight unification series Following the unification series, there were ongoing calls for Tyson and Spinks to fight, to erase any doubt about the identity of the "true" champion. In June 1988, the two champions faced off, and Tyson knocked out Spinks in 91 seconds. Tyson held on to his titles until February 1990, when he was knocked out by Buster Douglas. The titles remained unified until December 1992, when undisputed champion Riddick Bowe relinquished his WBC title. Heavyweight unification series The heavyweight unification series, also known as the Heavyweight World Series, was a sequence of professional boxing matches held in 1986 and 1987