Background-Clopidogrel was thought to be superior to aspirin for secondary prevention of vascular diseases in clinical trials. In this study we assessed the safety and efficacy of clopidogrel versus aspirin in real-world practice by using the Taiwan Stroke Registry. Methods and Results-Patients with ischemic stroke (2006-2016) on aspirin or clopidogrel for secondary stroke prevention were identified in the Taiwan Stroke Registry. Stroke recurrence and mortality rates in patients receiving aspirin (N=34 679) were compared with those receiving clopidogrel (N=7611) during a 12-month follow-up period. Propensity score matching and conditional Cox proportional hazards regression model were applied to control confounding factors with 6443 patients in each group. After propensity score matching stroke recurrence rates were comparable between groups with 223 patients in the aspirin (3.46%) and 244 in the clopidogrel group (3.79%) (hazard ratio=1.13 95% confidence interval=0.89-1.43 P=0.311). However the mortality rate was significantly higher in the clopidogrel group (362 patients 5.62%) than in the aspirin group (302 patients 4.69%) (hazard ratio=1.30 95% confidence interval=1.07-1.58 P=0.008). Results were consistent before and after propensity score matching. Conclusions-Clopidogrel was as effective as aspirin for prevention of recurrent stroke in real-world practice. However the mortality rate was significantly higher in the clopidogrel than in the aspirin group.