Perforated duodenal ulcer was clinically evaluated with respect to Helicobacter pylori infection and rate of recurrence in 38 ulcer patients perforated and 154 patients with non-perforated duodenal ulcer who visited our hospital in past 5 years and 6 months. The frequency of occurrence of H. pylori-positivity was 42.1% in patients with perforated duodenal ulcer, significantly lower than that of 92.9% in patients with non-perforated lesions. This result suggests that H. pylori is hardly involved in the development of perforated duodenal ulcer. The rate of recurrence was significantly lower for perforated duodenal ulcer than for non-perforated ulcer. In particular, perforated duodenal ulcer did not recur in the group on maintenance therapy with H2-recepter antagonists. Maintenance therapy using inhibitors of gastric acid secretion seems effective for the prevention of recurrence of perforated duodenal ulcer.