Adult patients with symptoms of gastric disease were randomly assigned to a treatment group (n = 103) or untreated control group (n = 89). The treatment group received 75 mg of roxatidine acetate hydrochloride at 9 PM and 12 to 13 hours later gastric juice secretion was measured with gastric x-ray films in both groups. Mean gastric juice secretion was significantly lower in the treated group (16.1 ml/12 hrs) than in the untreated controls (49.8 ml/12 hrs). Gastric juice suppression by roxatidine was 90% in patients with gastric ulcer, 74% in patients with duodenal ulcer, 63% in patients with gastritis, and 70% in patients with no evidence of disease. It is concluded that 150 mg of roxatidine daily would be adequate to treat patients with gastric diseases.