The divine, sacred, or magic plants which function as intermediaries between some Mexican Indians and their deities contain compounds that share some elementary psychoactive properties. Six families of sacred plants can be distinguished according to their effects: visionary, imagery-inducing, trance-inducing, deliriant, neurotoxic, and excitatory agents. After centuries of Western contact with Indian cultures and their magic plants, many of the botanical sources have been identified, chemicals considered responsible for their actions isolated, psychological effects described, and some specific neurochemical effects ascertained. While further specialized research may contribute historical, mythological, ecological, botanical, ethnological, phytochemical, psychopharmacological, and neurochemical information about each plant, it is clear that major advances can be made only by interdisciplinary groups. The capacity to design coordinated and sequential research strategies utilizing the methods of many fields should be the distinguishing characteristic of such groups. The growing field of ethnopharmacology emphasizes the need to understand the uses and effects of biodynamic plants in their cultural contexts as well as their chemical and pharmacological aspects. Social factors are considered to have an instrumental role in the modulation of biological effects of drugs. Many areas in ethnopharmacology are suitable for interdisciplinary study. Further historical documentation of plants not clearly identified is necessary as well as a reevaluation of the cultural meaning of the ancient use of psychoactive plants. Ethnological work is needed to deepen our understanding of the modem uses of plants within specific cultural contexts, especially the non visionary psychodysleptics. Further botanical and chemotaxonomical research is required to isolate bioactive chemicals especially from psychoactive Compositae, Labiatae, Leguminosae, and Solanaceae. The ecology of psychotropic plants especially in relation to animal behavior is a new field. The effects of the majority of the plants and their chemical constituents upon the mind is in an embryonic state of understanding and the study of their actions upon animal behavior, brain chemistry, and physiology promises to be a productive research area in the years to come. Besides the gain in knowledge, some of the practical implications of this type of research are to be noted, especially its relevance to the mind-body problem, source of tools for neuroscience, and possible applications in psychiatry. I hope that this review will stimulate studies that by coordinating different methods and strategies will yield a broader knowledge of the plants chosen by man to modify his mental functions, thereby expanding our understanding of such functions.