The use of such anti-platelet agents as aspirin and ticlopidine have not been approved in Japan for use in the prevention of the recurrence of cerebrovascular diseases that include cerebral infarction. Cilostazol is an anti-platelet agent indicated for the treatment of ischemic symptoms, including ulcer, pain, and cold sensation in chronic arterial occlusion, but it also has been confirmed to be effective over a placebo with respect to the prevention of cerebral infarction recurrences through a randomized, double-blind, placebo controlled, multi-center clinical trial (RCT). OBJECTIVES: To estimate the socioeconomic impact of cilostazol with concern to the prevention of cerebral infarction recurrences in Japan. METHODS: A Markov model was constructed to estimate the costs and the number of recurrences of cerebral infarction over a 5-year period for 50-year-old males. Annual average rates of cerebral infarction recurrences were derived from the RCT. QALYs were not considered due to a lack of utility data in Japan. Direct costs and indirect costs were calculated based on published data. Costs and the numbers of recurrences were discounted at 3% per annum. RESULTS: The cumulative number of recurrences of cerebral infarction over 5 years per 1000 people were 95 for the cilostazol group, and 272 for the no treatment group. The 5 year cumulative costs per person were 5,260,108 yen for the cilostazol group, and 11,374,638 yen for the no treatment group. Sensitivity analyses confirmed the robustness of these results. CONCLUSIONS: This study suggests that cilostazol is a valid form of treatment for the prevention of cerebral infarction recurrences in Japan from a socioeconomic standpoint.