OBJECTIVES: To determine the stroke and bleeding outcome among generic versus brand name warfarin recipients in a large cohort. METHODS: This is a nationwide population-based retrospective cohort study using administrative claims data National Health Insurance Research Database in Taiwan. We identified all patients who were diagnosed for AF and used generic or brand name warfarin alone between January 1, 2006, and December 31, 2010 (N=23,141) from the NHIRD. A propensity score matching approach is used to create a subgroup for further adjusting potential selection bias. Cox proportional hazards regressions were performed to estimate the risk of hospitalization for stroke and diagnosis of bleeding associated with the generic versus brand name warfarin recipients. RESULTS: We identified 12,944(55.94%) AF patients who received generic warfarin, and 10,197(44.06%) AF patients who received brand name warfarin. In the matched cohort, the event rate of hospitalization for stroke was 17.44 per 100 person-years for the generic warfarin group, as compared to 15.98 for the brand name warfarin group and the multivariate adjusted hazard ratios (HRs) for hospitalization for stroke of generic warfarin group was 1.15 (95% CI, 1.09-1.20) compared with brand name warfarin group. The adjusted HRs for critical site bleeding, definite bleeding, intracranial bleeding and gastrointestinal bleeding of generic warfarin group were 0.92(95% CI, 0.86-0.99), 0.94(95% CI, 0.90-0.99), 0.92(95% CI, 0.76-1.13) and 0.94(95% CI, 0.89-0.99) respectively in comparison to brand name warfarin group. Generic warfarin group was associated with statistically significantly higher risk for stroke when the prescribed daily dose of warfarin was higher than or equal to 2.5, the multivariate adjusted hazard ratio of generic warfarin group for stroke is 1.14(95% CI, 1.02-1.26). CONCLUSIONS: The generic warfarin recipients were at slightly but statistically significant higher risk of hospitalization for stroke and lower risk of bleeding in comparison to brand name warfarin group.