1 The effects of mianserin (60 mg) have been studied on nocturnal and pentagastrin-stimulated gastric secretion. 2 Mianserin reduced pentagastrin-stimulated gastric acid secretion by 38%, pepsin by 40% and secretory volume by 45% during a 1 h test. 3 Twelve-hour overnight secretion of acid was reduced by 37%, while secretion of pepsin was reduced by 43% and secretory volume by 51%. 4 No adverse effects were noted. 5 These findings, which achieve statistical significance, suggest the need for further study to evaluate the possible role of mianserin in the therapy of duodenal ulcer disease.