The effects of intraduodenal glucose infusions on pancreatic exocrine secretion were studied in anesthetized and in conscious rats with pancreatic fistula. In the anesthetized model a stimulating effect of glucose on pancreatic flow and bicarbonate output was evidenced. This effect was dose-related and depended in part upon osmolarity of the solution. No nervous mechanism could be demonstrated, while release of secretin in portal blood might be involved in the observed effect. In conscious rats an increase of bicarbonate concentration and output was observed after 30% intraduodenal glucose while protein concentration and output decreased very significantly. These effects persisted after vagotomy.