Widely recognized by anthropologists as the most powerful and widespread shamanic hallucinogen, ayahuasca has been used by native Indian and mestizo shamans in Peru, Colombia, and Ecuador for healing and divination for thousands of years. Made from the Amazonian vine Banisteriopsis caapiand the DMT-laden leaf of Psychotria viridis, ayahuasca is regarded as the embodiment of intelligent plant beings who can offer spiritual teachings and healing knowledge to those who respectfully engage with them. Many Western-trained physicians and psychologists now acknowledge that ayahuasca allows access to spiritual dimensions of consciousness, otherworldly realms and beings, and visionary experiences indistinguishable from classic religious mysticism. With contributions from leading psychoactive scholars Dennis J. McKenna, Ph.D., Charles S. Grob, M.D., and J. C. Calloway, Ph.D., on the ethnopharmacology, psychology, phytochemistry, and neuropharmacology of ayahuasca, Ralph Metzner provides a compre