Background: Atrial fibrillation is the most common sustained cardiac arrhythmia. It is a major cause of morbidity and mortality through an increased risk of thromboembolic stroke. Experimental as well as observational evidence suggests that n-3 polyunsaturated fatty acids may have antiarrhythmic effects. The objective of this study was to examine whether high intakes of fish and its very long-chain n-3 fatty acids eicosapentaenoic acid(EPA) plus docosahexaenoic acid(DHA) are associated with risk of incident atrial fibrillation. Methods: We used data from the Rotterdam Study, a prospective cohort study. At baseline, dietary intake data were available for 5184 subjects free from atrial fibrillation. Dietary intake was assessed using a semiquantitative food-frequency questionnaire, and incidence of atrial fibrillation was continuously monitored during follow-up. Cox proportional hazards model(adjusted for lifestyle and disease factors) was used to examine the associations between intakes of EPA plus DHA and of fish with atrial fibrillation. Results: After a mean follow-up of 6.4(±1.6) years, 312 subjects developed atrial fibrillation. Intake of EPA and DHA in the third textile compared with first was not associated with risk of atrial fibrillation(relative risk 1.18, 95%CI 0.88-1.57). Furthermore, no association was observed with intake of >20 g/d fish compared with no fish intake(relative risk 1.17, 95%CI 0.87-1.57). Conclusions: In this study, intakes of EPA and DHA and the consumption of fish were not associated with the onset of atrial fibrillation. This finding does not support that n-3 fatty acids have a general antiarrhythmic effect. Background: Atrial fibrillation is the most common sustained cardiac arrhythmia. It is a major cause of morbidity and mortality through an increased risk of thromboembolic stroke. of this study was to examine whether high intakes of fish and its very long-chain n-3 fatty acids eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) are associated with risk of incident atrial fibrillation. Methods: We used data from the Rotterdam Study, a prospective cohort study. At baseline, dietary intake data were available for 5184 subjects free from atrial fibrillation. Dietary intake was assessed using a semiquantitative food-frequency questionnaire, and incidence of atrial fibrillation was never monitored during follow-up. Cox proportional hazards model (adjusted for lifestyle and disease factors) was used to examine the associations between intakes of EPA plus DHA and of fish with atrial fibrillation. Results: After a mean follow-up of 6.4 (± 1.6) years, 312 subjects developed atrial fibrillation. Intake of EPA and DHA in the third textile compared with first was not associated with risk of relatives with a relative risk of 1.18, 95% CI 0.88-1.57). Conclusions : In this study, intakes of EPA and DHA and the consumption of fish were not associated with the onset of atrial fibrillation. This finding does not support that n-3 fatty acids have a general antiarrhythmic effect.