Recently streptokinase and urokinase have been shown to be useful in the nonoperative treatment of thromboembolic disease. Urokinase is emerging as a safer and more effective thrombolytic agent when applied either to definitively lyse spontaneous thrombosis where no underlying structural lesion is present or to serve as an adjunct prior to surgical reconstruction or transluminal angio plasty. The authors report a case of a high-risk cardiac patient in whom an embolic occlusion of the distal popliteal artery was completely recanalized by using a localized catheter infusion of urokinase. The source of the embolus was a left ventricular thrombus. No serious bleeding or proximal or distal embolic complications occurred. The potential hazards of fragmentation of the embolic source in the presence of systemic thombolysis, distal trifurcation embolization, and concomitant use of heparin are reviewed.