To investigate the association between atrophic gastritis and gastric cancer and to identify the risk and protective factors for the progression of atrophic gastritis to cancer, we conducted a prospective study on 5,373 subjects with neither cancer nor resected stomach who underwent gastroscopic examination and completed a life-style questionnaire. After an average of 6 years of follow-up, 69 gastric-cancer cases were identified, 65 from the subjects without atrophic gastritis and 4 from the subjects without atrophic gastritis. The presence of atrophic gastritis increased the risk of gastric cancer 2.19-fold, the risk trend increasing with the degree and the extension of atrophy [relative risk (RR) 1.60 for mild atrophy and 2.85 for moderate and severe atrophy]. Among the subjects with atrophic gastritis, family history of gastric cancer (RR 2.27) and a preference for spicy food (RR 1.84) increased the risk and self-administered meal controls, such as portion reduction (RR 0.44) reduction of salty food (RR 0.56) and the change to the consumption of easily digested food (RR 0.57) decreased the risk of gastric cancer. The results of this study suggest that atrophic gastritis increases the risk of gastric cancer but that dietary modification prevents the progression from atrophic gastritis to gastric cancer, regardless of pre-cancerous lesions.