In Mexico peyote was used seasonally in an agricultural-hunting religious festival, preceded by a ritual pilgrimage for the plant. Participants danced all night around a fire to the rasp-music of the shaman, as they ate the drug in this tribal celebration. Since about 1870 the cult has spread to the United States, particularly in the Plains, where nearly all groups use it. In the Southwest transitional region peyote became deeply involved in shamanistic rivalries and witchcraft, and in the Plains with war. A pre-peyote narcotic, the “mescal bean” (_Sophora secundiflora_) had there prepared the way for its introduction. The Plains cult is like the warriors’ societies of earlier times in some respects. The Kiowa, Comanche and Caddo were the chief agents of the spread of the cult throughout the entire Plains region to southern Canada and parts of the Great Basin. The standard ritual is an all-night meeting in a tipi around a crescent-shaped earthen mound and a ceremonially-built fire; here a special drum, gourd rattle and carved staff are passed around after smoking and purifying ceremonies, as each person sings four “peyote songs.” Various water-bringing ceremonies occur at midnight and dawn, when there is a “baptism” or curing rite, followed by a special ritual breakfast of parched com, fruit, and boneless meat. The Caddo-Delaware John Wilson had peyote visions that led him to modify the altar and ceremony; this new form has spread to the Caddo, Delaware, Quapaw, Osage and others. Wilson was one of a long line of Indian prophet-messiahs, and his “moon” has been somewhat exploited economically. The Oto teacher, Jonathan Koshiway, founded a Christianized version of peyotism which spread to the Omaha, Winnebago and others. An organization of confederated tribes known as “The Native American Church” grew out of Koshiway’s “Church of the First-born” (which latter spread to Negro groups also). The cult has had considerable legal difficulties. Praying and doctoring in meetings, and occasionally public confession of sins, are the major means for the liquidation of life-anxieties of this profoundly functional cult’s many present-day communicants. In the following pages we shall attempt to delineate the history of the study of the cult, the various botanical questions surrounding peyote, its physiological action and the various ethnological, psychological and historical questions involved in its diffusion.