The cumulative rate of symptomatic peptic ulcer (PU) was examined in a 10-year clinical follow-up study of 454 consecutive outpatients who had undergone diagnostic gastroscopy, from whom routine biopsy specimens were taken from the antral and corpus mucosa, and who were found to be ulcer-free before and at the time of this initial gastroscopy. During the follow-up period 34 (11%) of 321 patients who showed gastritis in the biopsy specimens at the initial gastroscopy had contracted symptomatic PU (18, 5, 7, and 4 cases of duodenal, pyloric, antral, and angular or corpus ulcer, respectively), which was verified by endoscopy. Only 1 (0.8%) of 133 patients with normal antral and corpus mucosa had contracted PU. It was calculated that the 10-year cumulative probability of PU was 10.6% (95% confidence interval (CI95), 7.2-14.0%) in the patients with gastritis, whereas this probability was only 0.8% (0-2.2%) in the patients who had normal antral and corpus mucosa in the initial specimens. The cumulative probability of PU was found to be highest, 27.3% (1.0-53.6%), in middle-aged men (41-60 years of age) who had chronic antral gastritis or chronic pangastritis (gastritis in both antrum and corpus). It is concluded that chronic gastritis precedes the appearance of PU and that the cumulative 10-year risk of PU is very low when both antral and corpus mucosa are normal but may be high if chronic gastritis is present.