There is a low risk area for gastric cancer in Jiangsu Province, China, where people frequently consume raw allium vegetables. As a first step epidemiological study to clarify the factors involved in the low incidence of gastric cancer, we conducted a comparative study of the ecological factors in a high risk area (HRA), Yangzhong, and a low risk area (LRA), Pizhou, using a questionnaire. Subjects were selected from the general population according to age and sex, and comprised 414 residents of the HRA and 425 residents of the LRA. Ecological factors were compared for the two areas by Cochran-Mantel-Haenszel method, age-adjusted. Smoking and drinking habits were found to be more common in the LRA. On the other hand, allium vegetables were consumed in the LRA much more frequently, with high consumption of raw vegetables, fruit, tomatoes, kidney beans and soybean products. People who consumed garlic en masse 3 times or more per week were 82% of men and 75% of women in the LRA, and 1 % of men and women in the HRA. The results of the survey suggest that frequent consumption of allium vegetables, in addition to other anticancer foods, may be a factor in low mortality for gastric cancer. J Epidemiol, 1999 ; 9 : 297-305