In a population-based case-control study of stomach cancer conducted in Warsaw, Poland, 464 cases and 480 controls were interviewed to evaluate the role of family history and other risk factors. A greater than threefold increase in risk was associated with a history of stomach cancer in a first degree relative (OR = 3.5; 95% Cl = 2.0-6.2), but no excess risk was seen with other forms of cancer. The risk associated with familial occurrence was not significantly modified by gender, age or ABO blood type, and did not vary with Laurén histologic classification. Our findings add to evidence for a familial predisposition to both diffuse and intestinal types of gastric cancer. Further studies are needed to identify the susceptibility genes and environmental exposures that may account for the familial tendency to stomach cancer.