46 patients over 60 years of age suffering from duodenal ulcer, 36 young patients with duodenal ulcer and 36 healthy aged persons (control group) have been examined after maximal pentagastrin stimulation. The results revealed that the aged patients with duodenal ulcer have significantly lower gastric secretion and acidity (BVO--87.7 +/- 36.8 ml/h, MVO--220.0 +/- 52.8 ml/h, BAO--4.23 +/- 2.63 mmol/h, MAO--25.43 +/- 8.39 mmol/h, PAO--30.34 +/- 12.09 mmol/h) than the young patients with duodenal ulcer (p less than 0.01-0.001). The volume of gastric secretion and the degree of acidity of the aged patients with duodenal ulcer are significantly above the reference value (BVO--71.6 +/- 19.5 ml/h, MVO--174.8 +/- 34.9 ml/h, BAO--1.84 +/- 0.96 mmol/h, MAO--16.58 +/- 4.02 mmol/h, PAO--20.73 +/- 3.08 mmol/l) of the control group of healthy aged persons (p less than 0.02-0.001). The suggestion is put forward that the differences in gastric secretion and acidity between the patients and the healthy persons above 60 years of age are one of the basic factors for development and/or persistence of the ulcerous process in old age.