This is a phase II multi-centre study in Europe in patients with stable coronary artery disease or troponin negative unstable angina undergoing elective PCI, to obtain the information on the safety and effects on various pharmacodynamic markers, of three doses of argatroban in combination with clopidogrel and aspirin, and to assess the results of argatroban and unfractionated heparin, both used in combination with clopidogrel and aspirin, on clinical outcomes, adequacy of anticoagulation, various pharmacodynamic markers (approximately 35 patients per group).