In Sri Lanka, as in India, two formally structured systems of medical service exist side-by-side. While Western-style biomedicine is believed to be useful, Ayurvedic medicine is also well established and commonly used. Underlying one explanation for the existence of plural medical systems is the idea that traditional and Western systems of medicine provide unique treatments for distinct problems, and patients having certain characteristics select them accordingly. A brief review of several studies in Sri Lanka suggest, however, that Western and Ayurvedic physicians practice medicine in similar ways, are selected for treatment of very similar symptoms, and from the patient's point of view are often indistinguishable from each other. A second structural explanation rests on the fact that, as institutions, Western and Ayurvedic medicine have effectively divided up territory and jobs to the satisfaction of each; this division allows for upward mobility, through medicine, for young people from different segments of society. Thus these medical systems persist, not because each provides something unique for patients, but because they provide access to status and power for the physicians themselves.