Hammar, E. T h e localization of precancerous changes and carcinoma after previous gastric operation for benign condition. Acta path. microbiol. scand. Sect. A, 84: 495-507, 1976. Sixty-five patients operated on for a benign gastric condition showed at re-operation in 9 cases precancerous changes, in 22 cases carcinoma in situ, and in 34 cases infiltrating carcinoma. T h e median time to elapse between the two operations was 20 years. l h e pathological diagnosis established at the first operation was most often benign duodenal ulcer. Investigation revealed in 9 cases precancerous changes and in 47 cases various grades of adenocarcinoma within the anastomosis. In 37 cases of Billroth I1 operations, 5 precancerous changes, 15 carcinomas in situ and 17 infiltrative cancers were located on the posterior gastric wall near the efferent small intestinal loop. I n these cases there were additional changes, one precancerous, 7 carcinomas in situ and two infiltrating cancers, situated against the cephalic part of the afferent small intestinal loop. Nineteen Billroth I1 patients had precancers or cancers at other sites within the anastomosis or gastric remnant. T h e remaining 9 cases of Billroth I, gastro-enterostomy and gastric Roux-en-Y procedures are too few t o allow conclusions concerning the localization of precancer or cancer in the anastomosis.