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Background & Aims: Dietary antioxidants, with additive and synergistic effects, can mediate the observed inverse association between plant food intake and risk of gastric cancer. We investigated whether the total dietary antioxidant potential of fruit and vegetables is an appropriate means of estimating the antioxidant impact on gastric cancer risk in a large population-based study., Methods: With a population-based case-control design, data were collected through face-to-face interviews with 505 newly diagnosed gastric adenocarcinoma patients and 1116 control subjects to assess dietary habits 20 years before interview. The total radical-trapping antioxidant potential (TRAP) of different plant foods was used to convert food frequency intake into antioxidant potential. Gastric cancer risk in groups exposed to higher levels of oxidative stress (smoking and Helicobacter pylori infection) was also examined., Results: Intake of antioxidant equivalents was inversely associated with the risk of both cardia and distal gastric cancer (odds ratio [OR], 0.65; 95% confidence interval [CI], 0.48-0.89 for the highest quartile of TRAP). Controlling for smoking, the inverse relationship between TRAP values displayed a clearer dose-response pattern. Never-smokers with the highest antioxidant intake had the lowest risk of cancer, 0.44 (95% CI, 0.27-0.71). Among H. pylori-infected subjects, the ORs varied between 0.66 and 0.41 for increasing levels of antioxidant potential., Conclusions: Our results suggest that dietary intake of antioxidants measured as total antioxidant potential is inversely associated with risk of both cardia and distal cancer. The innovative approach used in this study provides a new tool for investigating the relationship between dietary antioxidants and oxidative stress-related carcinogenesis.