A number of medication trials at major U.S. research universities are now, once more, legally exploring psychedelics' vast potential for treating various physical and psychological problems. These studies have been approved based on a medical model that considers psychedelics' effects as primarily biochemical, but some are also addressing wider humanistic and transpersonal implications for research and praxis. These studies may challenge the prevailing medical model of psychopathology that not only reduces humans to just their biology but also has led to widespread medical treatments through formularies that predominantly constrict, rather than enhance, human potential. Psychedelics offer great potential as tools for researching elusive areas within humanistic and transpersonal psychology, as well as powerful ways to facilitate humanistic and transpersonal growth.Psychedelics, a term which means mind-manifesting, was first used in 1956 by Humphry Osmond to define a group of substances with potent psychoactive properties that had previously been called by more pejorative names, such as hallucinogenics (i.e., causing hallucinations) and psychotomimetics (i.e., mimicking psychoses; Williams, 1999). Grinspoon and Bakalar (1979) defined psychedelics as nonaddictive substances that do not cause major physiological or psychological disturbances while reliably producing strong changes in mood, perception, and thought in a fashion similar to what is sometimes found in dreams, memory flashbacks, psychoses, and religious ecstasy. Although the boundary between psychedelics and other substances that may alter consciousness is not always clearly delineated, current consensus broadly includes a number of substances that are