James Toney claimed a historic win over John Ruiz to seize the WBA heavyweight title at Madison Square Garden.
Don King celebrates Toney's success with the fighter
Judges awarded the 12-rounder to the American by unanimous points decision, 116-111, 116-111 and 115-112.
Toney became only the third fighter after Roy Jones Jr and Bob Fitzsimmons to win a heavyweight crown after being a middleweight champion.
Ruiz, who first took the WBA belt from Evander Holyfield in 2001, retired after his sixth loss in 48 pro bouts.
He tried to clinch at every opportunity, but a controversial seventh-round knockdown put Toney in control.
The challenger landed a right hand to Ruiz's head and the champion stumbled back into the ropes and onto the canvas.
The referee ruled it was Toney's left foot stepping on Ruiz's right foot that had done the damage.
But Ruiz took a second trip to the canvas in the eighth round when he stumbled as Toney shoved him, an exchange that was ruled a slip.
By the end of the eighth round, blood was trickling from Ruiz's nose and also from Toney's mouth.
The exchanges slowed, but Toney stunned Ruiz with a powerful overhand right midway through the 11th round and landed a pair of combinations in the 12th to finish strongly.
Afterwards, Toney - who has 69 career wins, four losses and two draws - said he had set his sights on unifying the heavyweight division.
"I'll fight anybody at any time. I'm the WBA champion of the world and soon to be undisputed champion of the world."
"If I had a couple more weeks to prepare, I probably would have knocked Ruiz out. I knew whatever he did, it wasn't going to be enough.
"If there is boxing justice, we will never see him again. I'm sure Don King is going to throw him in the trash can where he belongs."
Ruiz did opt to bow out of boxing, but not without claiming he had won the fight.
"Toney┐s a tough guy to fight, but I connected a lot. I finished stronger and I won this fight," he said.
On the undercard, Panama's Vicente Mosquera gave Thailand's Yodsan Nanthachai his first loss in nearly 11 years with a unanimous 12-round victory to take the WBA super featherweight title
Mosquera knocked down the champion three times with a flurry of right-hand shots.
Luis Perez successfully defended his IBF super flyweight crown with a sixth-round knockout of Luis Bolano of Colombia.
It was the Nicaraguan's first fight since December 2003 but he dominated and knocked Bolano down twice before the decisive blow.