Using the concepts frontier and interface the introduction and spreading of modern Western medicine in Nepal and its relations to other medical systems are described and analyzed. Medical systems do not prevail in the same degree in all places; we may call the geographic areas of concentration the core areas or center(s) of medical systems and the remaining areas their periphery. The frontier of a medical system is defined as that part of the periphery where the presence of the system is increasing. The place of the frontier, its width and the forms in which a medical system appears at its frontier are determined by both internal dynamics and contextual factors. In non-socialist countries like Nepal the dynamics of modern Western medicine are characterized by three tendencies: centralization, expansiveness and a commercial and capitalist character. Some important contextual factors which have been shaping the frontier in Nepal are: migration, including tourism, labor-migration and trade; the role of foreign aid and geographical conditions. The situation at the frontier has an important influence on the nature of the interface between modern Western medicine and other medical systems. In the article Faith-healing, Ayurvedic medicine, Homeopathy and Tibetan medicine are described briefly and the interface between them and modern Western medicine is looked into.