In seventy-five out-patients with gastric and duodenal ulcer a comparative double-blind trial with pirenzepin against placebo was performed. The dose was 50 mg pirenzepin daily or placebo respectively, the duration of treatment being 4 weeks. The healing effect of pirenzepin in duodenal ulcer patients could be proven endoscopically and was statistically significant when compared with placebo (p less than or equal to 0.05). Strong evidence for the therapeutic efficacy of pirenzepin could be further demonstrated in both duodenal and gastric ulcer patients by measuring the marked reduction of ulcer size, even though statistical difference against placebo in gastric ulcers was not fully achieved. Pirenzepin was well tolerated by all patients, except for a mild case of diarrhoea which occurred in one patient. No patient complained of dryness of the mouth or of blurred vision.