Peyote is well known for its hallucinogenic effects; the plant contains at least 28 alkaloids, the principal one of which is mescaline (q.v.). Peyote figures prominently in the traditional religious rituals of certain North American Indian peoples, as well as in the current rituals (many adapted from traditional rituals) of the Native American Church (q.v.). The sale, use, or possession of dried mescal buttons or live plants is prohibited by law in many places, although a number of areas also provide exemptions for use in formal religious rites. The American Indian Religious Freedom Act (1978) is the primary legislation governing the religious uses of peyote in the United States.

Peyote is found only on limestone soils of the Chihuahuan desert of southern Texas and northern Mexico. Averaging about eight centimetres (three inches) wide and five centimetres (two inches) tall, the body of the peyote cactus is spineless, soft, and in most cases, blue green in colour.

The more common species, L. williamsii, has pink to white flowers in summer, the fruit ripening the following year. L. diffusa, more primitive, grows in a small area in central Mexico. Its flowers are white to yellow, and the body is yellow green.