Nonhuman primates provide the ideal animal model for discovering and examining further the mechanisms underlying human type 2 diabetes mellitus. In all aspects studied to date the nonhuman primate has been shown to develop the same disease with the same features that develop in overweight middle-aged humans. This includes the progressive development of the known complications of diabetes, all of which are extraordinarily like those identified in humans. In addition, for the development and evaluation of new therapeutic agents, the translation of findings from nonhuman primates to application in humans has been highly predictable. Both therapeutic efficacy and identification of potential adverse responses can be effectively examined in nonhuman primates due to their great similarity to humans at the molecular, biochemical, and physiological levels. This chapter provides guidance for the development and management of a colony of monkeys with naturally occurring type 2 diabetes mellitus.