Foster and Rondon met in Miami on April 7, 1972, in a unification bout. Foster became the undisputed world champion once again, by knocking Rondon out in the second round. In his next fight, he used what many critics have called one of the best punches in history to retain his title by a knockout in four against Mike Quarry. Foster then went up in weight and faced former and future world heavyweight champion Muhammad Ali, on November 21, 1972, in what was legendary referee Mills Lane's first bout of note as a referee. Foster lost to Ali by a knockout in the eighth, after being knocked down 7 times.
