Sugar Ray Leonard of Palmer Park regained the World Boxing Council welterweight championship last night when Panamanian Roberto Duran quit with 16 seconds left in the eighth round of their scheduled 15-round fight in New Orleans.

The official verdict was a technical knock-out. The Louisiana State Athletic Commission decided to hold up Duran's purse pending a medical examination of the former champion.

Afterward, Duran, 29, announced through an interpreter that he was retiring from boxing. "No more fighting," he said. "I don't want to fight anymore. I am retired from boxing."

The former champion also said that he suffered stomach and arm cramps at the end of the fifth round, cramps that grew worse until he quit -- "never before have I had cramps like this."

The sudden ending shocked Leonard, referee Octavio Meyran and most of the Superdome crowd watching a bout in which Leonard had the upper hand. He led by a total of five points through seven rounds on the scorecards of the three judges.

For Leonard, 24, former Olympic champion, the fight was worth a reported $7 million and avenged the first loss of his professional career, suffered in a narrow but unanimous decision to Duran at Montreal in June. Leonard's record is now 28-1-0.

Duran, 72-2, baffled his handlers. "I wish I could tell you what happened," said Ray Arcel. "I do not know. He just stopped."