Background The antiplatelet agent, cilostazol, is known to reduce the risk of subsequent cerebral infarction. However, the cost effectiveness of such treatment in comparison to aspirin has not been studied. Methods and Results A Markov model was developed to calculate the health outcomes and associated costs for 65-year-old patients with cerebral infarction who were treated with 200 mg/day cilostazol or 81 mg/day aspirin. Cilostazol was more effective, but also more expensive than aspirin. Cilostazol would extend quality-adjusted life years (QALY) by 0.64, while increasing life-time costs by approximately ¤1.1 million. The incremental cost-effectiveness ratio of cilostazol in comparison with aspirin was estimated to be ¤1.8 million per QALY. Conclusions The use of cilostazol to prevent recurrence of cerebral infarction appears to be cost effective. (Circ J 2006; 70: 453 - 458)