The high northern Andean valley of Huancabamba, Peru, is the centre of an extraordinary moon-oriented magico-religious healing cult, a fundamental feature of which is the nocturnal ingestion by patients and curandero of the mescaline-rich San Pedro cactus ( Trichocereous Pachanoi Brittonet Rose). Such is the notariety of the curanderos, or maestros, of Huancabamba that patients regularly arrive not only fromthe Peruvian coastal cities and the scattered settlements of the Maroñon river drainage area to the east, but from as far away as Argentina, Chile, Colombia and Ecuador. The healing process at Huancabamba involves two equally important phases. During the first, the maestro, under the influence of the San Pedro, divines the cause of the patient's predicament and prescribes a cure. The adherents of the cult believe that all of life's vicissitudes result from supernatural causes; hence commonly treated problems include both psychological and physiological disorders as well as chronic bad luck, marital troubles, sorcery and malevolent curses (Sharon 1978). The second phase of the curative process includes the treatment of the particular problem by means of folk remedies prepared from medicinal plants, the most efficaceous of which are said to grow in the environs of a number of sacred lakes known as Las Huaringas. Especially problematic cases are led by the maestro on pilgrimages to these lakes, located a hard day's walk above Huancabamba at an elevation of approximately 10,500 feet. In completing the pilgrimage and in bathing in the sacred waters, the penitent believes that he or she undergoes a metamorphosis, a spiritual regeneration that is profoundly curative (Schultes and Hofmann 1979, Sharon 1972, 1978). The dynamics of the Huancabamba cult have been discussed in some detail by a number of authors (Schultes and Hofmann 1979, 1980, Dobkin de Rios 1968, 1969, Sharon 1972, 1978, Friedberg 1959, 1960, 1963, 1980). The purpose of this paper is to introduce a number of novel ethnobotanical observations which I was able to make during my fieldwork in the region in 1981, including the discovery of a cactus previously unreported as an hallucinogen and a folk legend that offersevidence of the continuity of indigenous religious beliefs in the otherwise thoroughly "mestizada" culture of contemporary Huancabamba. For comparative purposes an account of the nocturnal curing ritual is presented.