Our study has several limitations. First, it was powered to evaluate differences in the response to clopidogrel among aspirin-resistant versus aspirin-sensitive patients. However, the sample size was inadequate to estimate the risk of myonecrosis associated with dual drug resistance. Second, the antiplatelet effects of aspirin and clopidogrel were evaluated at two points during a single 24-h period and may not reflect possible temporal fluctuations in individual responses. Nevertheless, these measurements reflect the extent of platelet inhibition just before and following PCI, when optimal inhibition is required. Third, the first blood sample was drawn from an arterial access and the second from a venous access. These conditions were, however, identical for both groups tested. Finally, our study was performed with a clopidogrel loading dose of 300 mg. Recent studies have indicated that a loading dose of 600 mg provides a more rapid and pronounced early response and reduces the rate of clopidogrel resistance (16,26- 27). However, most clinical efficacy data have been accrued with the 300 mg dose, and this is the only dose that is currently approved by the U.S. Food and Drug Administration (28).