This is a review of the chemistry, physiological and psychological effects, history, and present status of the ritual uses of peyote, a powerful narcotic, among American Indian tribes. The peyote cult is held to be 'a great intertribal religion' and a major cultural technique for alleviating individual anxieties. There is no illness for which peyote is not regarded as a specific cure, and peyote meetings of many groups incorporate public confession of sins as an important auxiliary 'mechanism for the liquidation of individual anxieties'.