Alpha amylase of pancreatic origin is cleared by the kidney more rapidly than the salivary isoamylase. To determine whether alterations in the ratio of pancreatic to salivary amylase in sera caused alterations in over all renal clearance, the clearance of amylase was measured before and after the exocrine pancreas was stimulated with a prolonged intravenous infusion of secretin plus cholecystokinin. Serum and urine samples collected prior to and following stimulation were analyzed for amylase activity and creatinine concentration. Amylase isoenzymes were separated using isoelectric focusing. Over all renal clearance of amylase and of the separated amylase isoenzymes were calculated as a percentage of the clearance of creatinine. The hormone infusion was associated with an increase in serum and urine amylase activities, this increase being mainly accounted for by pancreatic amylase. The renal clearance of the salivary and pancreatic isoamylases was not altered by the hormone infusion but the over all amylase clearance by the kidney rose from 2.31 +/- 0.74 to 3.42 +/- 1.46% of creatinine clearance. In some cases the renal clearance of amylase following stimulation entered the range considered diagnostic for acute pancreatitis.