This study was performed to investigate the pancreatic exocrine dysfunction in streptozotocin- induced diabetic rats. Changes in pancreatic enzymes secretion and in pancreatic enzymes content were observed. The output and the tissue content of amylase were significantly reduced in diabetic rats, while the output and the content of lipase were increased. Plasma secretin and cholecystokinin (CCK) concentrations of diabetic rats were significantly increased compared to those of normal rats. The altered pancreatic exocrine function was abolished by the exogenous insulin administration. The exogenous insulin also restored the increased plasma secretin and CCK concentrations. From the above results, it is suggested that, in streptozotocin-induced diabetic rats, anticoordinated changes in pancreatic enzymes secretion as well as pancreatic enzymes content are attributable to insulin deficiency and that the insulin deficiency is responsible for the increased plasma concentrations of both secretin and CCK. However, it is not clear whether the elevated plasma secretin and CCK concentrations played a direct role in changes of pancreatic exocrine function.