Objective To compare the efficiency and safety of aspirin-dipyridamole and warfarin in the prevention of thromboembolism in patients with nonvalvular atrial fibrillation(NVAF)and high risk factors.Methods One hundred and forty NVAF patients with high risk factors were randomly divided into two groups.Warfarin group[78 cases international normalized ratio(INR)2.0-3.0,for the patients older than 75 years,INR ranging from 1.6 to 2.5]and combination group(62 cases received aspirin 160 mg once every day plus dipyridamole 160 mg 3 times every day).The incidence of death,thromboembolism(including stroke and peripheral arteries embolism)and hemorrhage events were observed.Results Followed-up 12-28 months.In warfarin group,3 cases lost,2 cages had stroke,2 cases suffered from serious bleeding events,6 cases had minor bleeding events.In combination group,2 cases lost,6 cases had stroke,and 2 cases suffered from peripheral arteries embolism events,3 cases had minor bleeding events,but no serious bleeding events occurred.The incidence of thromboembolism in warfarin group wag,lower than that in combination group[2.7%(2/75)vs 13.3%(8/60),P<0.05].There was no significant difference of the bleeding rate between the two groups[10.7%(8/75)vs 5.0%(3/60),P>0.05].Conclusions Warfarin anticoagulative therapy is more effective than aspirin and dipyridamole antiplatelet dual therapy for the prevention of thromboembolism events in patients with NVAF and high risk factors.The major bleeding events in warfarin group occurs in patients with INR>3.0,so under intensive monitoring(INR 2.0-3.0),warfarin therapy is effective and safety.