Magic Johnson said he had tested positive for the AIDS virus and retired from pro basketball yesterday, shocking the sports world and leaving it without one of its true superstars.

In 12 sparkling seasons, Johnson showed the world a new way to play basketball and helped turn the pro game into the biggest sports success story of the 1980s.

Both he and his doctors stressed that he did not have AIDS, a disease of the immune system for which there is no known cure. Both also said that, while Johnson's playing days were over, he was far from through.

"I plan on going on living for a long time and I guess now I can enjoy some of the other sides of living," Johnson said at a news conference.

In becoming one of that select group of athletes known everywhere by just one name--"Magic"--Johnson led the Los Angeles Lakers to five NBA titles and helped lift the league to unprecedented success.

Unbridled Enthusiasm

The 32-year-old became one of sport's most recognizable figures for his smile and enthusiasm. The smile was still there yesterday, just faintly dimmed, and he said he would become a spokesman for AIDS groups, hoping to promote safe sex among youngsters.

"This is one of those things you think can't happen to you, but it can," Johnson said. "Sometimes you're a little naive about it and think it can never happen to you. You think it can happen to only other people. But it has happened, and my life will go on."

There was no immediate word how Johnson might have caught the virus, but at his news conference he stressed the issue of safe sex.

Lakers team physician Dr. Michael Mellman stressed Johnson's leaving basketball was not a reflection on his immediate physical condition.

Magic Urged to Retire

"What we witness today is a courageous act by a very special man," Mellman said. "Earvin Johnson has been infected with the AIDS virus. He is not ill in any way."

Mellman said the stress exerted on the body by professional basketball would not be good for Johnson's condition.

"The medical judgement is for Earvin to discontinue that. That is not normal activity," he said.

If Johnson remained composed as he announced the shocking news, others could not hide their emotions.