Between December 1968 and December 1983, the authors treated 30 patients requiring gastrectomy for carcinoma of the postoperative stomach. The patients were divided into two groups: 13 patients were operated on for primary carcinoma lesions (Group A) and 17 patients for benign lesions (Group B). Respective areas of carcinoma development and length of time from initial operation to the discovery of carcinoma of the postoperative stomach were investigated. A period of less than 10 years elapsed in 11 of the patients (84.6%) in Group A and advanced carcinoma developed in the area of the suture in many patients. In contrast, a period of more than 10 years elapsed in 16 of the patients (94.1%) in Group B. Early carcinoma was found in four out of six patients after 10-20 years, whereas advanced carcinoma was found in six out of 10 patients after more than 20 years. Carcinoma developed in the gastric remnant or the area of anastomosis in many patients. This suggests that carcinoma that is discovered within 10 years after operation might have been missed at the initial operation or might have recurred. We therefore defined carcinoma discovered more than 10 years after operation as primary stump carcinoma. To determine areas of carcinoma development and macroscopic findings, 91 patients with primary stump carcinoma (consisting of 18 of our patients and 73 patients from the Japanese literature) were compared with those with cancer in the upper third of the stomach (unoperated) (181 of our patients). Primary stump carcinoma was often found in the area anastomosed with the Billroth II operation, and primary early cancer in the gastric stump tended to be protuberant rather than excavative.(ABSTRACT TRUNCATED AT 250 WORDS)