The published world literature on the efficacy of pirenzepine, a new anti-muscarinic agent, in the treatment of gastric and duodenal ulcer is reviewed. In 12 prospective randomized double-blind placebo controlled studies pirenzepine was administered to 475 duodenal ulcer patients with an incidence of endoscopically proven healing of 74% when the daily dosage of the drug was 100 or 150 mg but of only 55% if the dosage of the drug was 75 mg or less. In 4 randomized double-blind placebo-controlled studies in which 84 patients with gastric ulcer were admitted, the healing rates were similar (50% when daily dosage of pirenzepine was 75 mg or less, 72% when the dosage ranged from 100 to 150 mg). When pirenzepine was compared to carbenoxolone or to cimetidine in the treatment of gastric and duodenal ulcer respectively, results obtained were comparable. Side-effects reported have been rare and of minor importance. Pirenzepine appears to be an effective drug for the short-term treatment of duodenal ulcer. More data are required for an assessment of short-term therapy of gastric ulcer and long-term maintenance treatment.