Antiplatelet therapy plays a key role in the prevention of complications related to coronary angioplasty and stenting (PCI) including procedure related myocardial damage. Aspirin and clopidogrel are now universally prescribed in patients undergoing these procedures. However, loading and maintenance doses have not been established and variation in individual response is emerging. New tests to assess the effects of these drugs are being developed but have yet to be incorporated into routine clinical practice. We will assess the effects of aspirin and clopidogrel in a consecutive series of patients undergoing angioplasty using new assays which can be carried out at the bedside. We will compare the results with alternative laboratory based tests and look for an association between the results, peri-procedural myocardial necrosis and subsequent cardiovascular events.