Leading causes of mortality and morbidity after kidney transplantation are cardiovascular diseases. One of the fundamentals of their prevention is the inhibition of platelet aggregation. Resistance to anti-platelet agents is a well-established phenomenon; however, its causes are yet to be clarified.Forty post-transplant patients, who received 75 mg clopidogrel q.d. as a prophylactic measure, were examined using optical aggregometry. Subsequently, logistic regression analysis was performed with 24 variables in order to expose possible causes of resistance.Sixty percent of patients (24) were resistant to clopidogrel therapy; effective thrombocyte inhibition could only be shown in 40% of them (16). Significant correspondence between resistance and variables could not be found.Clopidogrel resistance is expected to occur on a large scale in patients who underwent kidney transplant surgery. Thus, a key component of preventive therapy, which stresses the importance of discovering the cause of resistance so as to decrease mortality rates, is missing.