Adult Rana catesbeiana and premetamorphic tadpoles were injected with streptozotocin (200-1000 mg/kg, IP). Serum glucose and serum and pancreatic insulin-like immunoreactivity (ILI) were determined at various post injection intervals. Pancreatic beta islet histology or immunocytochemistry was also observed. Bullfrog adults became mildly hyperglycemic after streptozotocin injection but did not develop insulin deficiency. Hyperglycemic frogs had slightly elevated serum ILI concentrations and had pancreatic ILI comparable to that of the controls; hyperglycemic frog islets appeared indistinguishable from control islets. Tadpoles did not respond to streptozotocin.