In a follow-up study of 1000 patients, who were subjected to Billroth II resection for duodenal ulcer, the incidence and mortality of gastric carcinoma in a 22-30 year follow-up period were determined. Among the 423 survivors traced, 196 underwent gastroscopy and biopsy but carcinomas of the gastric remnant were not seen. Thus the prevalence was 0, not significantly different from the expected prevalence of 0.3. From all 1000 patients only 13 cases of gastric carcinoma were identified. This is not significantly different from the expected number of 10.6 calculated by the life table method and indirectly standardized for age, sex, place of residence and time. Even more than 15 years after operation thegastric cancer risk was only slightly increased (observed/expected = 7/4.8 +/- 1.48), but this was not significant statistically. Of 522 deaths 13 were due to gastric carcinoma, which was not significantly different from the expected number of 10.2. These epidemiological data show that individuals subjected to Billroth II resection for duodenal ulcer hardly have a higher risk of gastric carcinoma than the general population within the first decades after operation. Thus proplylactic endoscopical monitoring will be unrewarding.