It is now clear that diabetes millitus is not a disease in classical sense but is genetically heterogeous froup of disorders whitch share glucose intolerance in common. Genetic heterogeity, the concept that diabetes can have many different causes, was first suggested by the existence of rare genetic syndomes with diabetes, etnic differences of clinical features, and genetic heterogeneity in animal models. This paper describes the background for genetic heterogeneity of diabetes mellitus which has major implications for the research and care of diabetic patients since the precise etiology, risk of complications and genetic counselling are likely to vary among these diggerent disorder that result in diabetes. Key words: diabetes mellitus-genetic heterogeneity-model of inheritance-genetic counselling-autoimmune process. Amhad H. Asdie;Laboratorium/Unit Pelayanan Fungsional Ilmu Penyakit Dalam, Jurusan Kedokteran Medik Fakultas Kedokteran Universitas Gadjah Mada/Rumah Sakit Umum Pusat Dr. Sardjito, Yokyakarta
