Depression and anxiety were measured during the course of a double-blind, placebo-controlled trial of the histamine H2-receptor antagonist, ranitidine (150 mg twice daily), in patients suffering from duodenal ulcer but free of systemic disease. There were 25 patients in the ranitidine group (mean age: 33.2 years) and 28 in the placebo group (mean age: 37.2 years). In both groups there was a highly significant and progressive decrease in depression and anxiety scores over the 4 weeks of treatment. There were no instances of mental confusion. In our group of otherwise physically healthy patients, ranitidine appeared to be free of neuropsychiatric complications.