This article describes our initial experience with intraoperative infusion of the fibrinolytic agent streptokinase. Five patients with various complications of atherosclerosis manifested by limb-threatening ischemia were treated by balloon-catheter thromboembolectomy followed by intra-arterial streptokinase infusion. In each patient viability of the involved extremity was questionable after removal of all thrombus accessible to the balloon catheter. Fibrinolytic therapy was used when operative arteriography showed residual thrombus distal to the popliteal artery. All patients were systemically heparinized during the operation, and three patients were maintained on anticoagulants during the initial postoperative period. A streptokinase solution containing 750 U/ml was infused intra-arterially proximal to the residual thrombus. The total dosage ranged from 20,000 to 100,000 units per patient. This treatment was considered successful in all five patients, as documented by return of palpable pulses, audible Doppler flow signals where none was present prior to infusion, and operative arteriography. There were no complications related to intraoperative streptokinase infusion. We conclude that intraoperative fibrinolytic therapy is a safe adjunct to catheter thromboembolectomy. The observed improvement in limb perfusion can be attributed to lysis of thrombus in the distal arteries that could not be retrieved with the balloon catheter. Laboratory studies are in progress to establish precise indications for intraoperative streptokinase and to determine the most effective dosage and rate of administration.