Sixty-nine patients with symptomatic and endoscopically diagnosed gastric or duodenal ulcers received treatment with either pirenzepine 100 mg or cimetidine 800 mg one hour before bedtime in a prospective randomised, double blind study. Fifty-five patients completed the six weeks treatment period of whom 13/15 (87%) gastric ulcers and 13/16 (81%) duodenal ulcers, healed with pirenzepine compared to 8/11 (73%) gastric ulcers and 10/13 (77%) duodenal ulcers treated with cimetidine for the same period. The differences in healing rates between pirenzepine and cimetidine were not statistically significant. Pirenzepine 100 mg administered at night is therefore an effective treatment for gastric and duodenal ulcers.