Use of urokinase to treat heparin-associated thrombocytopenia and thrombosis in one patient is described, and various treatments proposed for this syndrome are discussed. A 56-year-old man received an intravenous bolus dose of heparin sodium at his local hospital and was transferred to another institution for treatment of suspected pulmonary embolism; he had received heparin two weeks earlier during coronary angiography. The patient's platelet count was reported to be normal before heparin administration. When embolism was confirmed, heparin was discontinued and streptokinase was given for 24 hours. Heparin infusion was then restarted at 1000 units/hr and continued for four days. Platelet count on admission to the second hospital was 47,000/cu mm; 12 hours later it was 19,000/cu mm, and it remained low despite platelet transfusions. Five days after admission, deep-vein thrombosis developed in the left leg. Heparin was discontinued and urokinase and warfarin were started. Urokinase was infused at 320,000 IU/hr for 12 hours and continued at dosages of 160,000-320,000 IU/hr for a total of 40 hours. The initial warfarin sodium dose was 15 mg, followed by a dosage of 10 mg/day. Symptoms of deep-vein thrombosis improved within 12 hours and platelet count increased after heparin was discontinued. If it is recognized early enough, heparin-associated thrombocytopenia can be reversed by discontinuation of heparin. Transfusions of platelets are of little benefit. Dipyridamole, cyclo-oxygenase inhibitors such as aspirin, and protamine sulfate may be useful. Long term anticoagulation with warfarin is recommended to prevent recurrent thrombosis.(ABSTRACT TRUNCATED AT 250 WORDS)