The role of atrophic gastritis of the gastric corpus (fundal atrophic gastritis) as a high-risk factor was investigated by studying operative findings and follow-up data on 690 patients with benign gastric diseases recorded at the Osaka Cancer Registry. The extent of fundal atrophic gastritis was determined by the endoscopic Congo red test. The patients were followed-up from the time of endoscopic examination (1968 to 1976) to December 31, 1987. The vital status of 654 patients (94.8%) at the end of the observation period was determined. During the follow-up period, 22 patients were found to have gastric cancer. The extent of fundal atrophic gastritis was shown to be closely related with the risk of developing gastric cancer. Patients who had been diagnosed as having severe fundal atrophic gastritis showed significantly higher risk of gastric cancer than patients who had been diagnosed as having little or no fundal atrophic gastritis (5.76-fold, calculated with adjustments for age, sex and the follow-up period). A positive linear relationship was found between the risk of developing gastric cancer and the extent of fundal atrophic gastritis. The observed number of gastric cancers was compared with the expected number calculated from the incidence in Osaka Prefecture. Analysis of the results showed that the observed and expected numbers of gastric cancers in patients with severe fundal atrophic gastritis were 11 and 4.8, respectively, the ratio of observed to expected numbers being 2.3 (p < 0.05). These findings indicate that severe fundal atrophic gastritis is a major risk factor for gastric cancer.