Cats appear to be one of the few non-human species that develop a type of diabetes mellitus analogous to human Type 2, or non-insulin-dependent diabetes mellitus (NIDDM). In this review, some current theories on diabetogenesis are discussed. In both cats and human beings, Type 2 diabetes is characterized by impaired insulin secretion due to a functional defect in pancreatic beta-cells, and insulin resistance. In both species, amyloid deposition occurs in pancreatic islets and is derived from the newly discovered pancreatic hormone islet amyloid polypeptide (IAPP), or amylin. Amylin also reduces insulin secretion and induces insulin resistance. Thus, the hypothesis of amylin being intimately involved in the pathogenesis of human and feline Type 2 diabetes appears justified. Obesity is a frequent concomitant problem in feline and human Type 2 diabetes and contributes to the insulin resistance characteristic of the disease.