Abstract: AIM: To observe the clinical safety and effectiveness of warfarin on the prevention of stent thrombosis after percutaneous coronary intervention (PCI). METHODS: Of the 78 patients who were treated with stents, 48 patients with bare-metal stents were enrolled in group A and 30 patients with drug-eluting stents in group B. The clinical manifestations of the two groups were similar. All patients received routine treatment and adjusted dose of warfarin (international normalized ratio 1.5-2.0). We observed and compared the effect of warfarin on acute cardiac events and complications during and after the first month. RESULTS: During the first month, no occurrences of angina and acute myocardial infarction were seen in all the patients, and there were no hemorrhagic complications. After the first month, one case of angina was observed in group A and three cases in group B, but no acute myocardial infarction was seen in either group A or group B. Stenosis was observed in other coronary arteries, but no thrombosis and in-stent restenosis were found at stents. CONCLUSION: Warfarin may prevent acute cardiac event after PCI. With proper dosage, this medication is safe and effective for both bare-metal stents and drug-eluting stents.