The flora of South America is very rich in hallucinogenic plants used in many places by the local population for various purposes. Several researchers, including especially SCHULTES, have provided contributions to the present use of these plants.Almost nothing of these plants, such as Ayahuasca (Banisteriopsis caapi) is known in terms of use in early times, although some authors accept that they were used by the Incas. The Incas herb remains indicate an extensive arsenal of medicinal plants, including plants with hallucinogenic properties. A biggest number has been described by the chroniclers, but the knowledge in their manuscripts have not yet been fully explored; many of the plants described have not yet been identified. A precise examination of the medicinal plants, which are used at different locations nowadays by local population, can give an important contribution to the slogan of this problem, but this will still require a lot of work.