In order to consider whether the line of thought regarding operative indication should be changed in the light of the recent decrease in the number of operations for peptic ulcer following the introduction of H₂-receptor antagonists, a total of 104 cases of gastroduodenal perforation, including 87 cases of peptic ulcer which had been examined in our department and related facilities, were investigated with regard to the following factors. (1) The mean times elapsing between ulcerative perforation and surgery were 26.1 hours and 9.0 hours in cases where bacteria were present (+) and absent (-) in ascites, respectively. In addition, the ratios of cases showing poor postoperative infectious control was 53.3% and 1.5% in groups where 24 hours or more, and less than 24 hours, elapsed after perforation, respectively, suggesting that 24 hours is a borderline period. (2) Among five cases which showed a good general condition even though free air (+) was found on the simple abdominal radiogram, whose abdominal symptoms were localized and in whom epiboly of the perforation was expected to result in conservative treatment, four cases showed remission of symptoms in 24 hours or less after treatment, while one case showed no improvement of the symptoms, necessitating surgery 24 hours after treatment, although the postoperative course was uneventful. The above results indicate that conservative treatment is possible for some cases such as ours, especially cases of acute ulcerative perforation in younger patients. This led us to the consideration that the course during the 24-hour period after perforation should be observed before deciding on the operative indication.