Relative risk (RR) and cumulative risk of gastric cancer (GCA) were calculated for different grades of atrophic gastritis (AG) of the antrum and body. Cross-sectional data on the occurrence of AG in a representative population sample (371 subjects), and Finnish Cancer Registry data on GCA were used in the calculations. The RR was increased significantly in severe AG of the antrum and the body (18.1 and 4.6 times, respectively), but not significantly in the less severe grades of AG. As a risk factor, severe antral and body gastritis were independent of each other. The cumulative risk, i.e., the probability of contracting GCA within the following 10 years in age groups 50-54 . . . 70-74 years was calculated to vary from 2.3% to 9.3% and from 8.7% to 31.9% in severe antral AG and from 0.9% to 4.5% and from 3.6% to 16.6% in severe body AG in males and females, respectively.