A systematic analysis of the cellular components of intestinal metaplasia (i.e., goblet cells with or without brush border cells and Paneth cells) was performed in endoscopic gastric biopsies from 984 patients without gastric ulcer or carcinoma; 359 Swedish and 625 Japanese patients. The Japanese patients, matched for age and sex, had twice as much intestinal metaplasia as the Swedes. The frequency of goblet cells and columnar cells with brush (absorptive) border increased with increasing age in both ethnic groups. Complete intestinal metaplasia (i.e. the presence of at least two or all three cellular components) was twice as frequent in the Japanese. This may reflect differences in the environment (including food habits) of the gastric mucosa in the two populations. Structural mucosal changes (i.e. pseudo-villus formations) were found more than twice as often in the Japanese. Since pseudo-villus changes occurred as often as goblet cells and brush border cells in both groups, it is suggested that the above-mentioned mucosal structural change should be considered for inclusion among the histological criteria of intestinal metaplasia of the stomach. Incomplete intestinal metaplasia (i.e. the occurrence of goblet cells without the other cellular components) occurred in similar proportions in the two populations. The present findings support the theory that incomplete intestinal metaplasia may be a para- rather than a preneoplastic phenomenon.