Ayahuasca, or hoasca, whether known by these names, or any of numerous other designations, has long been a subject of fascination to ethnographers, botanists, psychopharmacologists, and others with an interest in the many facets of the human relationship with, and use of, psychoactive plants. With its complex botanical, chemical, and pharmacological characteristics, and its position of prime importance in the ethnomedical and magico-religious practices of indigenous Amazonian peoples, the investigation of ayahuasca in its many aspects has been an impetus to the furtherence of our scientific understanding of the brain/mind interface, and of the role that psychoactive plant alkaloids have played, and continue to play, in the quest of the human spirit to discover and to understand its own trancendent nature.