Patients on warfarin treatment pose particular problems when undergoing percutaneous coronary intervention with stent implantation (PCI-S), because of the poor definition of the optimal antithrombotic strategies to be adopted both peri-procedurally and during the 4 (or more) weeks after PCI-S, when dual antiplatelet therapy with aspirin and clopidogrel is recommended. In the absence of solid evidence-based data, no definite recommendations for the management of this patient subset are currently given in the guidelines on percutaneous coronary intervention issued by the most prominent Cardiology Associations. Indeed, a high variability has been reported in the current antithrombotic strategies, which may consist in either the temporary substitution of warfarin by dual antiplatelet treatment or the combination of warfarin and aspirin or clopidogrel or both. Peri-procedural bridging therapy with either intravenous unfractionated or subcutaneous low-molecular-weight heparin is also variably carried out. Purpose of this registry is to determine in patients on warfarin treatment undergoing PCI-S: 1) the contemporary peri-procedural and medium-term antithrombotic management; and 2) the relative safety and efficacy of the various antithrombotic regimens.