The starting material consisted of 357 subjects with gastric polyps found at endoscopy. Histologically, these cases were divided in four groups: adenoma, 8%; hyperplastic polyp, 34%; foveolar hyperplasia, 21%; and inflammatory polyp, 36%. Of these 210 patients were for various reasons no longer available for follow-up study. Endoscopic follow-up study for about 8 years (range, 5-15.5 years) was performed in 147 patients. At the follow-up examination, in 103 patients morphologic signs and in 92 of these immunological and functional signs of pernicious anaemia were examined. The prevalences of severe atrophic gastritis affecting mainly the body mucosa (26%), parietal cell and/or intrinsic factor blocking antibodies (25%), low serum vitamin B12 levels (8%), and overt pernicious anaemia (treated and new cases, 11%) were significantly higher than in equal numbers of age- and sex-matched controls examined in a similar manner. Gastric cancer was found in 3 (2%) cases followed up for more than 5 years. This is seven times the expected incidence, with a 95% confidence interval of the risk ratio (1.5-20.9). The high frequency of gastric cancer and pernicious anemia emphasizes the importance of long-term endoscopic follow-up study of patients with gastric polyps.