Walter Pahnke was a minister, physician, and psychiatrist who attended Harvard in the early 1960s. He earned an MD from Harvard Medical School, a BD (now MDiv) from Harvard Divinity School, a PhD from Harvard Graduate School of Arts and Sciences, and a Harvard psychiatric residency.

On April 20, 1962 Pahnke conducted an experiment as part of his Ph.D. thesis in Religion and Society under his thesis advisors Timothy Leary and Richard Alpert. In this experiment, ten students from Andover-Newton Theological School were given 30 mg psilocybin and ten an active placebo (nictonic acid - vitamin B6) in a religious setting to see whether entheogens could engender a genuine religious experience. Nine out of ten of the students reported religious or mystical experiences while only one of ten in the placebo group reported the same. Among those who participated in the study were Leary and Huston Smith, professor of philosophy at MIT and respected religious scholar.

In 1967, Pahnke joined the team at the Maryland Psychiatric Research Center in Spring Grove, Maryland, conducting psychedelic therapy sessions with LSD and later DPT with terminal cancer patients as well as people suffering from alcoholism and severe neurosis. There he worked with therapists Stan Grof, Bill Richards, and Richard Yensen among others and served as director of the project from 1967 until 1971. In 1971, Walter Pahnke died in a scuba diving accident in Maine.