The Cayo Santiago rhesus monkey colony was established in 1939 by transporting 400 adult animals from India to Puerto Rico. This colony has existed since that time with no significant manipulation and careful documentation of the matriline inheritance since 1959. In 1984, intravenous glucose tolerance tests (IV-GTT) were carried out on animals derived from two of the six troops that exist on Cayo Santiago. The results of this study suggest that about 20% of the adult population exhibited carbohydrate intolerance, overt diabetes and/or hyperinsulinemia. The objective of this project is to further characterize the carbohydrate impairment found in the initial IV-GTT by: (1) carrying out the frequently sampled intravenous glucose tolerance test (FS-GTT) in the 45 animals of Groups M and J that showed an abnormal IV-GTT in 1984; (2) to establish the degree of obesity in animals showing impaired carbohydrate intolerance; and (3) to document the presence of an amyloid glycoprotein and/or islet cell antibodies in a selected group of animals. These studies will establish whether the rhesus monkey from Cayo Santiago is a primate model for spontaneous adult onset diabetes and prediabetes.