It is difficult to normalize plasma glucose for a prolonged period of time by s.c. injection in experimental animals. The goal of this study was to determine the feasibility and the dosage of insulin needed to maintain 24-h normoglycemia in streptozotocin-diabetic Syrian hamsters with a s.c.-implanted osmotic minipump. The pumps, which release insulin at a constant rate, were replaced every 14 days with fresh pumps for as long as 52 days. A high insulin dose (1 U/kg/h) was required to normalize plasma glucose and fatty acid concentrations, water and food consumption, urine output, and body weight.