The charts of 79 patients who required femoral arterial (FA) thrombectomy after cardiac catheterization were reviewed. Fifteen patients (19%) had poor pulses after thrombectomy and 2 had an extremity amputated. One thousand consecutive patients undergoing cardiac catheterization were also studied to prospectively determine the safety and efficacy of systemic fibrinolytic therapy for treatment of FA thrombosis. Among these, 771 patients underwent retrograde arterial catheterization, including 31 patients with left-sided obstructive lesions who had undergone transarterial balloon dilation procedures with large catheters. All patients were given heparin at the time of arterial cannulation. Patients who had a pulseless extremity 4 hours after catheterization continued to receive heparin therapy for 24 to 48 hours. If the extremity continued to have no palpable pulse and the systolic blood pressure was less than 50% of that in the contralateral leg, intravenous streptokinase infusion was begun. The overall incidence of FA thrombosis was 3.6% (28 of 771), including 39% (12 of 31) of all patients undergoing transarterial balloon dilation procedures; 97% (27 of 28) of patients weighed less than 14 kg and the majority weighed less than 10 kg. After an average treatment period of 33 hours, 16 patients continued to have a pulseless extremity and were treated with streptokinase for an average duration of 13 hours. Normal pulses and systolic blood pressure returned in 14 (88%) and were nearly normal in 1 other patient (6%). The incidence of bleeding at the arterial puncture site was 25% and was highest in the patients who had a transarterial balloon dilation procedure. No serious complications occurred.