Dietary pattern analysis is an alternative and complementary approach to identify the relationship between diet and the risk of chronic disease. This study was aimed at investigating the associations between dietary patterns and the risk of gastric cancer in Japan. Using baseline data from a prospective study of 20,300 men and 21,812 women, we conducted factor analysis and identified 3 major dietary patterns, healthy, traditional and Western, and calculated the factor scores of each pattern for individuals. During 10 years of follow-up, 400 cases of gastric cancer were identified. We found an inverse association between the healthy pattern and gastric cancer risk in women [rate ratio for highest quartile (RR) = 0.56; 95% CI = 0.32–0.96; p for trend = 0.03], but not in men. In contrast, the traditional pattern was significantly associated with the increased risk of gastric cancer in both genders (for men, RR = 2.88, 95% CI = 1.76–4.72; for women, RR = 2.40, 95% CI = 1.32–4.35). The Western pattern was not associated with risk. These associations persisted in histologic subtypes. Our findings support the idea that the healthy pattern decreased the risk of gastric cancer among females, while the traditional pattern increased the risk in both genders. © 2004 Wiley-Liss, Inc.