Clinical characteristics were examined in 49 patients with perforated gastroduodenal ulcer treated in the hospital during the recent 4 years. The mean age of the patients with perforated duodenal ulcer was younger than that with gastric ulcer. Many cases of perforated duodenal ulcer occurred at night and in autumn or winter. On the contrary those of perforated gastric ulcer had no such characteristics. Sixty-six point seven, per cent of the patients with perforated duodenal ulcer had no previous history of any ulcer and the patients with a previous history of an ulcer did not have taken H2 blocker at the manifestation. The rate of detection of free gas on abdominal X-ray was 86.7% for the perforated gastric ulcers and 77.1% for perforated duodenal ulcers. No association of preoperative leucocytosis were comparatively predominant in aged patients. The positive ratio of bacteria in the peritoneal cavity increased when the time lapse from manifestation of symptoms to surgery was longer than 6 hours. Forty-nine patients recieved extended gastrectomy and the mortality rate was 0%. Two patients with perioperative sepsis were both aged, had longer time lapse from manifestation of symptoms to surgery, and had no leucocytosis.