Ayahuasca is a tea made from two plants native to the Amazon, Banisteriopsis caapi and Psychotria viridis, which, respectively, contain the psychoactive chemicals harmala alkaloids and dimethyltryptamine. The tea has been used by indigenous peoples in countries such as Brazil, Ecuador and Peru for medicinal, spiritual and cultural purposes since pre-Columbian times. In the 20th century, ayahuasca spread beyond its native habitat and has been incorporated into syncretistic practices that are being adopted by non-indigenous peoples in modern Western contexts. Ayahuasca's globalization in the past few decades has led to a number of legal cases which pit religious freedom against national drug control laws. This paper explores some of the philosophical and policy implications of contemporary ayahuasca use. It addresses the issue of the social construction of ayahuasca as a medicine, a sacrament and a "plant teacher." Issues of harm reduction with respect to ayahuasca use are explored, but so too is the corollary notion of "benefit maximization."