A summary is presented of human self-experiments or psychonautic bioassays of pharmahuasca--capsules containing crystalline N,N-dimethyltryptamine (DMT) plus harmine, as well as combinations of other psychoactive tryptamines with other beta-carbolines. The 1967 Holmstedt-Lindgren hypothesis of the ayahuasca effect--oral psychoactivity of DMT consequent to monoamine-oxidase (MAO) inhibition from simultaneous ingestion of beta-carbolines--has been confirmed by eight self-experimenters. Results of a total of some 70 bioassays are summarized and the literature on this subject is reviewed (with 66 references and one table).