In a complete reversal of his previous positions, Timothy F. Leary admitted yesterday that "LSD may be creating a new race of mutants."

In a talk at Manhattan Town Hall in New York, the former lecturer in Clinical Psychology said. "I am going to stop using the drug, and I am going to ask you to stop."

Leary hastened, however, to praise the gains which have resulted from experiments with LSD and other hallucinogens. "LSD cures alcoholism accelerates learning, and may be helpful in treating all forms of mental illness," he said. But because of possible harmful side-effects of the drug, he advised development of further methods to produce the psychedelic effects without using LSD.

"By simply using lights, combinations of sound, and the stroboscope we can get the marijuana effect, the mescaline effect and the LSD effect," Leary explained.

"I don't know how the psychedelic explosion can be stopped," said Leary "and I don't even know if it's good or bad, but I do know that our society is not so perfect that it cannot stand a generation of experiment."

Leary's doubts about the psychedelic movement did not extend to marijuana. "The only problem with marijuana," he said, "is that it is almost free. It is not addictive, nontoxic, and less dangerous than alchohol."

Widespread use of marijuana would undoubtedly harm the liquor business, Leary contended, if the wild cheap weed were made readily available to the public.

He predicted that within five to ten years people will be licensed to use marijuana "just as they are now licensed to use the automobile."

Leary is presently free on bail, pending appeal of a federal sentence of 30 years in prison for illegal importation of marijuana to Texas. Last week his rented estate in Millbrook, N.Y. was raided by the police, who found marijuana on the premises and arrested Leary and 28 others.