Michael Hollingshead was born in Britain and studied philosophy. In 1960 he was living in New York, working as the executive secretary of the Institute for British American Cultural Exchange, when he ordered a gram of LSD from Switzerland under the pretext of using it for controlled studies. He mixed the LSD into a mayonnaise jar full of icing, making 5,000 one-teaspoon doses of 200 ug each. He had never tried LSD and, after his first strong experience, he contacted Aldous Huxley who suggested he get in contact with Timothy Leary to discuss LSD's potential.

In September 1961, he met Leary in Cambridge and was invited to live in Leary's house as well as teach a course at Harvard. Shortly thereafter, he introduced Leary to LSD. He participated in the Concord Prison Experiment with Leary, Cohen and Meztner in 1962. For the next few years, he worked with psychedelic therapists, lived at Milbrook with Leary and Alpert, and eventually ended up in London where he opened the World Psychedelic Center in 1965. At the Center, Hollingshead sold copies of psychedelic books and continued to "spread the word" about LSD. He became known as one of the Johnny Appleseeds of LSD.

Among those Hollingshead was supposed to have turned are: Timothy Leary, William Burroughs, John Lennon and George Harrison.