Between August 1983 and December 1987, 23 patients received a 30-minute intraoperative, intraarterial infusion of streptokinase (seven patients) or urokinase (16 patients) because of residual thrombus or persistent ischemia or both after thromboembolectomy. Ages ranged from 21 to 77 years (mean, 58 years). In 15 patients intraoperative lytic therapy was part of the initial operation, whereas in eight patients intraoperative lytic therapy was performed during a secondary operation to treat thrombosis of a recently placed graft. Seven patients in the latter group had hypercoagulable conditions (five had heparin-induced thrombosis; one had protein C deficiency; one had polycythemia with thrombocytosis). Improvement after intraoperative lytic therapy was seen on angiography performed after infusion in 13 of 17 (76%) patients in whom angiography was performed both before and after intraoperative lytic therapy. Grafts in 12 of these patients remained patent without additional intervention, and in one graft thrombus formed again. In contrast, among four patients without angiographic evidence of improvement, thrombus formed again in four grafts (p less than 0.004). Intraoperative lytic therapy was considered successful in 74% of instances (17/23), including four of seven patients with hypercoagulable states. Three of six patients whose grafts failed had major amputations, whereas there were no amputations after successful infusions. Twelve patients were heparinized after intraoperative lytic therapy. Ten patients in this group were considered treatment successes, and two were considered treatment failures. Three of 11 patients not heparinized after intraoperative lytic therapy were considered treatment failures. Four hematomas occurred in the former group and none in the latter (p less than 0.03). No hematomas occurred in the heparin-induced thrombosis group in spite of anticoagulation with sodium warfarin (Coumadin). Only one hematoma occurred within 6 hours of intraoperative lytic therapy, and thus it was attributable to the infusion. We conclude that intraoperative lytic therapy is an effective adjunct to manage residual thrombus or persistent ischemia or both after lower extremity revascularization. Postinfusion angiography is of prognostic value. Heparinization after intraoperative lytic therapy seems beneficial but significantly increases the risk of bleeding complications.