The purpose of this study is to define the incidence of complications at the arterial access site after cardiac catheterization. The influence of the arterial access site on these complications was identified, as were the clinical characteristics of these problems. A total of 8,797 cardiac catheterizations were performed over the 3-year period of this study. Diagnostic catheterizations and percutaneous transluminal coronary angioplasties (PTCAs) were included, and the arterial access site was identified. Diagnostic catheterizations were performed via the brachial artery (group I, n = 3,137 or the femoral artery (group II, n = 4,055). PTCAs were also performed via the brachial artery (group III, n = 32) or the femoral route (group IV, n =1,573). Ninety-five major vascular complications occurred during the course of this study. The frequency of complications was higher with brachial artery catheterization when compared with the femoral route. PTCA was associated with a higher rate than diagnostic studies. Brachial artery complications were primarily arterial thromboses, which were easily diagnosed and treated. Femoral complications were more complicated, difficult to identify, and associated with significant morbidity.