Streptokinase was injected directly into the arterial tree following balloon-catheter embolectomy on 13 occasions to remove residual thrombus that could not be mechanically retrieved in 12 patients with imminent limb (ten patients) or kidney (two patients) necrosis. Effective lysis, confirmed by arteriography, pulse return, and increased ankle pressures, was achieved in 11 trials (85%). Bleeding complications, minor in three patients and severe in two patients, were ascribed to systemic lysis although other factors were contributory. One of five deaths was related to therapy. Six limbs were salvaged. The average total dose of streptokinase used, 110,000 units, was given in intermittent boluses of 25,000 to 50,000 units injected below a clamp placed to temporarily occlude distal circulation. Safe application of this technique requires intraoperative monitoring of coagulation parameters, aggressive replacement therapy, and prudent patient selection. This preliminary experience suggests that intraoperative lytic therapy (1) is an effective method for clearing thrombus not amenable to mechanical extraction and (2) may improve patency and tissue salvage.