In this open, prospective study we assessed the prevalence of antiplatelet resistance among patients subjected to intracoronary stent implantation. In patients treated with aspirin + thienopyridine (N = 32), platelet reactivity index (PRI) significantly decreased after 2 and 7 days of dual antiplatelet treatment in comparison with the same patients on aspirin monotherapy (P<0.001, both). After 7 days of aspirin + thienopyridine treatment, insufficient antiplatelet response was observed in 28% (9/32) of the patients. High interindividual variability in response to aspirin + thienopyridine treatment emphasizes the significance of thienopyridine resistance, while the influence of statins on such a treatment should be reassessed.