Presented herein is an ethnographic description of the Makushi Amerindians of Guyana and study of the biomedical efficacy of traditional remedies employed by the Makushi. One of the primary controversies in the field of ethnomedicine is whether a therapeutic intervention using a traditional remedy owes its success in controlling or alleviating symptoms of illness to its biomedical efficaciousness or, alternatively, to the placebo effect. Some researchers in ethnomedicine are inclined to believe that traditional remedies always work because indigenous pharmacopoeias are hoped to be the panacea for the world's incurable diseases. Other researchers, however, take the other extreme and tend to argue that herbal concoctions only serve psychosocial needs of the patient and act as placebos without addressing the biomedical needs of the individual This dissertation takes a pathway between these polarities. I first provide geographical, ethnohistorical, and contemporary ethnographic data on the Makush Amerindians. Then I discuss the sociocultural system of illness causation, classification of illness, sick-role, the decision-making process towards treatment and treatments administered to the patient, including the psychosocial support the patient receives during the duration of the illness bout, as seen from the Makushi vantage point. Following a 'universal methodology' proposed by several medical anthropologists, I present data on the preparation and administration of traditional remedies, voucher specimens of plants utilized in these remedies, the botanical identifications of these plants, and the relevant pharmacological literature and pharmacological databases (i.e., NAPRALERT, Internet Grateful Med) that contain evidence of known bioactive properties in these species which are congruent with their uses (or reported uses) as remedies among my Makushi subjects In the conclusion, I evaluate both the biomedical efficacy of a relatively small section of the Makushi pharmacopoeia which I examined as well as the usefulness of this proposed universal methodology and other suggested methodologies, such as prospective and retrospective case reporting, in conducting this study under the field conditions I encountered in the Rupununi savannas of Guyana