OBJECTIVE: To determine the cost-effectiveness of thrombosis prevention with Clopidogrel versus Ticlopidine in Russia. METHODS: Clinical efficacy of Ticlopidine 250 mg daily versus Clopidogrel 37,5 mg daily was evaluated in a comparative clinical trial including 30 days follow-up of 70 patients with thrombophilia. Clinical efficacy was measured by percentage reduction in spontaneous platelet aggregation (SPA) that was considered to be a prognostic indicator for thrombosis. Costs for medication were calculated. cost effectiveness ratio (CER) was defined for both drugs, and incremental cost-effectiveness ratio (ICER) was determined RESULTS: Mean percent SPA reduction from baseline level was 63,3% in the Clopidogrel group, and 48,8% in the Ticlopidine group. The mean cost for 30 days of Clopidogrel treatment was 1221 rub (42,1$) compared to 795 rub (27,4$) for Ticlopidine. The CER for Clopidogrel was 19,2 rub (0,66$) per 1% SPA reduction; for Ticlopedine - 16,2 rub (0,56$) per 1% SPA reduction. ICER for Clopidogrel group versus Ticlopidine group was 29,17 rub (1,01$) per 1% SPA reduction. CONCLUSION: Clopidogrel 37,5 mg daily achieved a greater percentage reduction in SPA than Ticlopidine 250 mg daily. Costs for Clopidogrel were higher than for Ticlopidine, though ICER suggests that additional effect can be achieved relatively inexpensively. For final conclusion, the safety of both drugs should be taken into account.