In the Amazonian provinces of Peru indigenous shamanistic practices are preserved among the mestizo population. Practitioners who call themselves vegetalistas (from which the term Vegetalismo may be formed) believe that certain plants, which they call doctores (plant-teachers) have spirits from which knowledge about this and other worlds may be gained, if these plants are ingested under certain conditions involving sexual segregation and a diet that may extend from six months to several years. Several of these plants have pychotropic properties, or contain important biodynamic compounds. Two of these plants, Banisteriopsis caapi (Spruce ex Griseb.) Morton and Psychotria viridis Ruiz & Pavon, are used in the preparation of ayahuasca, a psychotropic brew with the aid of which vegetalistas contact the spirit world in order to diagnose and cure illnesses. Other plant-teachers may also be added to the basic ayahuasca preparation. This book presents information about shamanic initiation, and of the spirit world of vegetalistas. Shamanic knowledge and power transmitted to the neophytes have two principal manifestations: 1) magic melodies or icaros which are learned from the spirits and used to perform various shamanic tasks, and 2) a magic substance received from the spirits and carried by vegetalistas in their chests, and which is used in the extraction of magic darts or virotes, shot by evil sorcerers, and which are believed to be one of the causes of illness. This book also provides information about ayahuasca sessions and the ideas held in the Peruvian Amazon about illness and its treatment.