Neonatal rats receiving streptozotocin at birth resulted in an acute but transient hyperglycemia for about ten days. This early transient hyperglycemic condition led to a reduced body weight gain in the suckling period but body weights were normalized by day 42. Streptozotocin pups had higher pancreatic wet weights and pancreatic protein and DNA contents at day 16 as compared to control pups, but not thereafter. At day 16, pancreatic trypsinogen in streptozotocin pups showed a transient increase over control pups but amylase and lipase were similar in the two groups. No difference was observed between the streptozotocin pups and the control group in their pancreatic lipase and trypsinogen concentrations after 16 days. In contrast, pancreatic amylase concentrations were lower in streptozotocin pups from day 18 to day 42 but the difference between the groups was significant only from days 18 to 24. Insulin supplementation of streptozotocin pups for four days in the neonatal period restored the pancreatic amylase concentration to the control level at days 18 and 20. These results indicate that acute streptozotocin administration at birth to neonates affects subsequent exocrine pancreatic development, particularly that of amylase, and that exogenous insulin attenuated the effect.