Secretion patterns of gastric lipase and pepsin were studied in duodenal ulcer patients before and after vagotomy and in healthy subjects following continuous administration of pentagastrin in graded doses. The lipase output increased in response to pentagastrin stimulation in similar fashion as that of pepsin. The output of the two enzymes were correlated with each other and with hydrogen ion output. Evaluation of dose-response relationships showed that in duodenal ulcer patients the secretion of gastric lipase and pepsin is more sensitive to pentagastrin stimulation than that of hydrogen ions.