Most of the medical research on diabetes mellitus is carried on by employing animal models of this disease. Even a casual review of the titles of articles cited in the reference section at the end of any research publication is enough to leave the impression that most of the studies on diabetes mellitus are carried out on animals. An animal model of diabetes remains as the only useful model of the disease if solutions to the etiology of diabetes and its complications are to be found. Animal models of diabetes can be subdivided into two broad categories: spontaneous diabetes and experimentally induced diabetes. The chemically induced diabetic animal is the most common model of diabetes mellitus employed in research. Early after injection of the diabetogenic agent, a condition of chronic hyperglycemia is permanently established. The derangement in blood metabolites is severe in uncontrolled, chemically induced diabetes.