Toney won the IBF and lineal middleweight titles by knocking out Michael Nunn in eleven rounds in May 1991. Toney, who entered as a 20-to-1 underdog, was down on all three judges' scorecards, but landed a left hook that put Nunn on the canvas in the eleventh round, and eventually scored a stoppage victory. The win also earned Toney the Ring Magazine Fighter Of The Year award. Toney continued a regular fight program over the next 18 months at middleweight, before outgrowing the division, where he made several successful yet disputed defenses. The most noteworthy was Toney's split decision win over Dave Tiberi in a fight that many experts feel Toney lost. The decision was so controversial that it prompted United States Senator William Roth of Delaware to call for an investigation into possible corruption in the sport. Toney also won a split decision title defense against Reggie Johnson in June 1991, retained his title with a draw against former WBA champ Mike McCallum in December 1991, and again against McCallum, this time by a majority decision, in December 1992. The McCallum fight would be Toney's last as a middleweight.