A speech Richard Alpert was scheduled to give tonight at Phillips Exeter Academy has been cancelled.

The former assistant professor of Clinical Psychology and Education had been invited three weeks ago to speak before the Inquirers' Society, a nonsectarian religious discussion group. He was to talk on the religious implications of hallucinogenic drugs.

W. Ernest Gillespie, Acting Principal of Exeter, initially approved Alpert's lecture, but changed his mind after the publication of an article describing Alpert's background in Saturday's Exonian, the student newspaper.

Consulted with Psychiatrist

Gillesple withdrew the invitation Saturday afternoon, after consulting with the school psychiatrist, Dr, Duncan Stevens. A telegram sent to Alpert at Cambridge address had not been delivered as of yesterday afternoon. Alpert was reported to be at his home in Millbrook, N.Y., but was unavailable for comment.

In a statement issued Saturday, Gillespie said "Richard Alpert's advocacy of the use of drugs to produce detachment from reality and other hallucinations led me to conclude that such a lecture could not be justified without the approval of the medical department.

"Consultation with Dr. Stevens brought emphatic agreement with my doubts about the advisability of allowing Dr. Alpert to speak here," the statement continued.

Students at Exeter were surprised by Gillespie's decision because the administration had recently advocated free speech at the school, according to David Finely, Associate Editor of the Exonian. James Jackson, Editor of The Worker, a Communist semi-weekly, delivered lecture on April 9, at which time school officials publicly justified his appearance.

Alpert was dismissed from the Harvard Faculty last May for violating a University agreement by giving consciousness-expanding drugs to an under graduate.