Amylase isoenzyme analysis by agarose gel electrophoresis and lipase concentration by radioimmunoassay were performed in 98 consecutive hyperamylasemic patients. Total pancreatic (P-type) isoamylase was elevated in 89% of patients with clinical evidence of pancreatitis, and in only 11% of those without pancreatitis. Of 43 patients in whom the clinical diagnosis was obscure, 44% demonstrated an increase in pancreatic amylase and three (7%) had an increase in salivary (S-type) amylase. Lipase concentration by radioimmunoassay correlated well with lipase activity (r = + 0.69, P less than 0.05) and was as effective as amylase isoenzymes in distinguishing patients felt likely to have pancreatitis from those who were unlikely. Amylase isoenzymes or serum lipase concentration may be useful tests in the laboratory evaluation of hyperamylasemia when the etiology is obscure.