Recombinant human tissue-type plasminogen activator (rt-PA) was infused intraarterially at 0.1 mg/kg/h for 1-6 1/2 hours in 25 patients with lower extremity thromboembolic occlusions (13 thrombosed arteries, 12 thrombosed bypass grafts). Occlusion duration ranged from 1 hour to 21 days. Thrombolysis occurred in 23 of 25 patients (92%). Time to lysis varied from 1 to 6.5 hours, with an average time of 3.6 hours. Twenty of 23 patients (87%) in whom thrombolysis was successful benefited clinically from thrombolytic therapy. Twelve of 23 patients (52%) required secondary procedures to maintain arterial segment patency. In 15 of 25 patients (60%) fibrinogen levels were maintained above 50% of baseline values. No major complications directly attributable to rt-PA infusions occurred. rt-PA is a potent, relatively fibrin-specific thrombolytic agent that can achieve rapid thrombolysis while usually avoiding the profound systemic fibrinogenolysis associated with currently available thrombolytic agents.