Pinklon Thomas knocked Mike Weaver down in the first round, then kept his WBC heavyweight championship with a one-punch knockout in the eighth round of their scheduled 12-rounder tonight.

"After I knocked him down in the first round," Thomas said, "I knew I could get him down again, if I hit him properly."

He did. He hit him flush with a overhand right. "I never saw it coming," Weaver said.

He said that, while on the canvas, he felt fine and was waiting to get up at the count of nine. "My head was clear," he said. "But when I said, 'Get up,' my legs said, 'Stay here.' "

He struggled up as referee Carlos Padilla counted 10, then fell backward. It was ruled a knockout at 1:42 of the eighth. Thomas weighed 220, Weaver 221.

"I don't know what I'll do now," Weaver, 32, said. "I don't know whether I'll say goodbye to the sport or hang in there."

Thomas (26-0-1 with 21 knockouts) hadn't fought since winning the title on a 12-round decision over Tim Witherspoon Aug. 31. Last October, Thomas had retinal surgery on his right eye.

"I've always had a good right hand, it's just never been exposed," he said. "I want peanut-head Larry Holmes."

But earlier today, Holmes signed to defend his International Boxing Federation title in September against Michael Spinks, the undisputed light heavyweight champion.

Thomas got $400,000 for the fight, which drew about 3,000 and was seen on Home Box Office. Weaver (27-11), a former WBA champion, got $200,000.

Earlier, heavyweights Trevor Berbick and Witherspoon won impressively.

Berbick peppered David Bey with nearly 25 straight punches in the 11th round to score a technical knockout in a scheduled 12-rounder and win the U.S. Boxing Association title.

Berbick fought a dull fight for 10 rounds, then, midway through the 11th, staggered Bey with a right-left combination. Bey, bleeding from the nose, sagged onto the ropes.

Berbick closed in and threw combinations, landing solidly until referee Mills Lane stopped it at 2:30 of the round.

Berbick, the last man to fight three-time heavyweight champion Muhammad Ali, is 28-4-1 after scoring his 22nd knockout. Bey, whom Holmes knocked out March 15, is 14-2.

Witherspoon, the North American Boxing Federation champion, staggered James Smith several times and scored a lopsided unanimous decision in 12 rounds.

Witherspoon staggered Smith with rights in the second, fourth, ninth and 10th rounds.

There were no knockdowns, but Witherspoon buckled Smith's knees in the fourth round. Smith landed 99 punches, Witherspoon 315. All three judges scored it 119-109. Witherspoon is 20-2, Smith 15-4.

Should Holmes win in September, he would match Rocky Marciano's 49-0 record. Marciano, the only heavyweight champion who never lost, quit after knocking out light heavyweight champion Archie Moore Sept. 21, 1955. Holmes knocked out heavyweight Leon Spinks, brother of Michael, in three rounds June 12, 1981.