The amazonic brew ayahuasca, with strong psychoactive properties, and which has been used probably for millennia by Amazon tribes as their main "medicine", is currently being used by some groups in cities in Latin America and abroad by people seeking curative effects or transcendent and meaningful experiences. At the same time, research on its effects in treating depression and in neuroimaging is being carried out. The brew is made of a blend of at least two different plants cooked together that potentiate each other: the stem of a vine, called ayahuasca proper (Banisteropsis caapi), and the leaves of a bush, chacruna (Psychotria viridis). In this chapter, the ritual is described and the pharmacodynamics of the brew are discussed, as well as some of its effects in the brain and in the subjective experience of the self. Two vignettes of patients in analytical psychotherapy are presented to illustrate its effects. Reflections on the risks and benefits of its use are then shared. © 2010 Springer Japan.