The epidemiology and dynamics of gastritis were studied in a representative sample of an urban population of Estonia. The sample consisted of 227 subjects 15-69 years old who were examined by direct-vision endoscopic biopsy, and the data were subjected to dynamic evaluation by stochastic principles. The prevalence of antral gastritis (64%) was similar to but that of body gastritis (62%) higher than that in other population samples studied by us. Correspondingly, the prevalence of atrophic antral and body gastritis was high: 38% and 37%, respectively. The prevalence of atrophic gastritis in the antrum and body increased significantly with age. On the other hand, no sex dependence of gastritis could be demonstrated. The prevalence of gastritis mainly affecting the body (32%) was significantly higher in the present than in the other Estonian sample (19%) studied by us. Complete loss of normal body glands was found in 14 subjects, and in 8 of these the antrum was normal or only slightly altered (type A gastritis). The prevalence of gastritis mainly affecting the body increased significantly with age, whereas that of gastritis mainly affecting the antrum decreased. Dynamic evaluation disclosed two basic dynamic patterns similar to those found in other population samples: the age-specific prevalences of gastritis increased with age according to the Poisson process, and gastritis started in the antrum at a younger age, but its progression was more rapid in the body mucosa. Dynamically, the chief finding of the sample was markedly more rapid progression of the body gastritis than in other samples, which explains the high prevalence of gastritis mainly affecting the body mucosa (type A gastritis) in the present series.