Introduction: An increasing amount of evidence indicates that platelet reactivity, despite a standard anti-thrombotic therapy, is a potential risk factor for recurrent myocardial ischemia in patients with coronary artery disease. We now hypothesize that this condition, measured by collagen-epinephrine (CEPI) or collagen-ADP (CADP) closure times (CT) by Platelet Function Analyzer (PFA-100), may predict the recurrence of coronary events after percutaneous coronary intervention (PCI). Materials and methods: CEPI and CADP-CT were measured 30 8 h after PCI in 175 consecutive patients admitted with a diagnosis of stable angina (n=94) or acute coronary syndromes (n=81) and prospectively followed up for a mean period of 6 months. We stratified the patients in accordance to both the CEPI-CT (< or > 190 s), reflecting the intensity of cyctoxygenase inhibition by aspirin and the distribution into quartiles for CADP-CT. Results: CEPI-CT < 190 s as well as CADP-CT < 82 s were associated with a higher rate of clinical recurrence (hazard ratio 8.5, p < 0.001 and 22.9, p < 0.001, respectively). Multivariate analysis after adjustment for other risk factors confirmed that the lowest CADP-CT quartile significantly correlates with the risk of recurrent coronary events (hazard ratio 36.5, p < 0.01), as welt as CEPI-CT < 190 s (hazard ratio 6.7, p=0.01). Conclusions: An enhanced platelet function after PCI when measured under high shear rates by PFA-100 is an independent predictor of a worst clinical outcome, even during a short term follow-up and may help in patients risk stratification. (c) 2005 Elsevier Ltd. All rights reserved.