The world’s most renowned authorities on the botany and chemistry of hallucinogens have produced an exhaustive study of psychoactive flora. The properties of the plants and the use made of them by man are examined and detailed by botanist Richard Evans Schultes and chemist Albert Hoffman. Their text is accompanied by many illustrations, over a hundred of which are in color. Complementing the botanical lexicon is a reference guide indicating where each hallucinogen is used, by whom and under what circumstances, how it is prepared, and what the effects are. In an ethnographic survey, Schultes and Hoffman examine the use of fourteen major hallucinogenic plants by peoples of non-industrialized societies who have passed down religious rites from generation to generation. Schultes vividly describes the pilgrimages made to gather the sacred plants; the rites, prayers, songs, and dances associated with their use; and the behavior of the users. Hoffman’s lucid explanation of the plant chemistry is his unique contribution to the biochemistry of psychotropic substances.