The aim of this study was to evaluate the efficacy of cilostazol for prevention of stent thrombosis compared with ticlopidine. Cilostazol is a potent antiplatelet agent with less serious side effects. However, few data are available about the effect of cilostazol in preventing stent thrombosis after coronary stent implantation. Four hundred ninety patients selected for elective stent placement were randomized to receive aspirin plus ticlopidine (n = 243) or aspirin plus cilostazol (n = 247) for 1 month. Clinical and laboratory evaluations were performed at regular interval. There were no differences in baseline characteristics between the 2 groups. During the first 30 days after stent implantation, major cardiac events or adverse drug effects were similar between the 2 groups: ticlopidine (2.9%) vs cilostazol (1.6%) group, p = NS; stent thrombosis (0.4% vs 0.8%, p = NS, respectively), myocardial infarction (0.4% vs 0.8%, p = NS), severe leukopenia (1.2% vs 0%, p = NS), severe thrombocytopenia (0.4% vs 0%, p = NS), and cerebral hemorrhage (0.4% vs 0%, p = NS). Adverse effects led to drug withdrawal in 7 patients in the ticlopidine group (2.9%) and in 5 in the cilostazol group (2.0%). There was no death during the follow-up period. Thus, aspirin plus cilostazol may be an effective antithrombotic regimen with comparable results to aspirin plus ticlopidine after elective coronary stenting.