A hallucinogenic decoction, called Yage or Yaje, in Colombia, Caapi in Brazil and Ayahuasca in Ecuador and Peru, is regularly used by many native tribes for centuries. It is prepared mainly from the trunk of a climbing plant Banisteriopsis Caapi. The sections of this vine are boiled with the aerial parts of other plants (such as Psychotria viridis or Diplopterys cabrerana). This very bitter drink contains powerful psychotropic alkaloids of a beta-carboline type such as harmine, harmaline, and especially d-tetrahydroharmine, most often accompanied by N,N-dimethyltryptamine (DMT). The absorption of 2 to 3 dL of this preparation causes approximately 20 to 30 min of delay, some vivid hallucinations that form colourful visions similar to those obtained with mescaline, psilocybin or LSD. The time of action for drugs which may last from 2 to 6 hours depends on the nature of the mixture of beta-carbolines and the protection and synergic action that develops between DMT and the latter. Such hallucinogenic preparations - many of them having an emetic, purgative or cathartic action and facilitating dream induction - are traditionally used to access these modified states of conscience that the natives consider favourable to travel to the world of spirits. The witch doctors or shamans of these American tribes are specialists after long and difficult learning. Discovered in the early 20th century, similar events to Ayahuasca consumption are still observed in other parts of the world. The use of peyolt (Lophophora williamsi) in some northwest Mexico tribes and the traditional use of iboga root (Tabernanthe iboga) in central West Africa are the most typical examples. Escaping the native tradition, churches - based on the ritual consumption of Ayahuasca were born in Brazil from 1930 with the influx of settlers in the Amazon basin. Despite differences, all these practices share similar similarities derived from the integrative nature of Ayahuasa's action itself. Scientific study of these practices could help us to better understand the biochemical mechanisms responsible for certain mental diseases such as schizophrenia. Ayahuasca alkaloids are generally considered to be narcotics under the law. According to countries, plants and preparation itself are not systematically banned. Since the use of Ayahuasca quickly spreads outside Brazil, this new "wild consumption" represents the related risks of prohibition. In recent years, "churches" in Europe and the USA have been seized and their members arrested. Many cases are pending before the courts, yet a decision of the Dutch court on 21 May 2001 acquitted the followers of one of these churches by invoking the constitutional right to freedom of religion. Some pseudo-scientists took the issue to bring a “legal diversification” through the selection of plants that are more easily accessible. Some of the alternative culture crops usually are offered via the Internet, either the drugs itself or the basic ingredients to make the beverage itself. Various recepies are proposed. A forum address brings together Internet users who can confront their experiences. Currently, there is a tendency to use any psychotropic plant regardless of its basic toxicity. A project to treat Peruvian drug addicts is intended to use as curative treatment not only Ayahuasca, but also a whole range of plants known as "depurative", some of them are recognized as toxic. The introduction of this type of practices outside its traditional framework raises concerns about manipulation and fraud that allow some individuals to benefit from the modified state of consciousness induced by this natural drug, especially since certain psychotropic medicines of the Western pharmacopoeia can interact strongly with the effects of alkaloids occuring in Ayahuasca.