Kinetic models of the glucose regulatory systems are being developed for man and other animals in collaboration with several experimental groups. These include models of the distribution, metabolism, and receptor binding of insulin using data both radioiodinated and native insulin models of the production and utilization of glucose as elucidated by tracer studies with labeled glucose alanine and lactate, and models of the role of insulin in the control of glucose utilization and production. The models are being used to gain insight into the metabolic changes which take place in various conditions of altered glucose homeostasis such as obesity and diabetes. Kinetic models of the glucose regulatory system, including the insulin subsystem, are being developed for man and other animals from collaborative studies with experimental groups and from data in the literature.