Before the year's end, he was undefeated in eleven bouts (winning all by way of early round knockouts) and fighting for the world title for the first time.

In 1989, he retained the title six times, beating Freddie Delgado, Frankie Swindell, Mike Sedillo and former WBA champion Leslie Stewart, among others.

In 1990, he retained the title three times before the end of the year, beating Mario Melo and former Michael Spinks challenger Jim McDonald, among others.

He rolled through the competition en route to securing an opportunity to fight for the vacant WBO heavyweight championship the following year against Bert Cooper.

Moorer eventually joined Lou Duva's team, and was trained by Georgie Benton for three fights in 1993, including a 10-round decision win over former champion James "Bonecrusher" Smith.

Moorer then parted ways with the Duvas and Benton, and hired New York-based trainer Teddy Atlas in late 1993.

In his first defense of those belts, on November 5, 1994, Moorer faced 45-year-old George Foreman, who lost his last fight for the vacant WBO heavyweight title to Tommy Morrison.

Moorer was ahead on all three judges' scorecards entering the 10th round, when Foreman hit him with a number of long-range jabs.

Then, suddenly, a short right hand caught Moorer square on his chin, gashing open his bottom lip, and he collapsed to the canvas.

South African Francois Botha travelled to Germany instead and beat Schulz with another close decision to claim the title, but he was stripped of it when he tested positive for illegal substances shortly after.

In a brutal one-sided bout, Moorer, leading on the cards going into the 12th, ended with a flourish, knocking Botha out 18 seconds into the final round.

In March 1997, Moorer retained his belt with a 12-round decision over previously undefeated Vaughn Bean before parting ways with trainer Teddy Atlas, with whom he'd been experiencing increasing tension since the beginning of their professional relationship.

Moorer was knocked down five times before ringside doctor Flip Homansky advised referee Mitch Halpern to stop the bout in round eight.

After a layoff of almost a year, he returned on July 3, 2004, losing a ten-round unanimous decision to Eliseo Castillo in Miami, Florida.

In December of that year, Moorer rallied from a severe deficit on the scorecards to hand former cruiserweight champion Vassiliy Jirov his first knockout loss.