We describe three pediatric patients in whom locally infused streptokinase at a dose of 50 U/kg/hr was used successfully to treat thrombosis in a major artery, a major vein, and a systemic-to-pulmonary arterial graft. Complications, including hemorrhage and distal embolization, were minimized by careful monitoring of the coagulation status of the blood and by avoiding rapid infusions. Selective thrombolytic therapy appears to be as effective in infants as in adults. Because the dose required is reduced, the incidence of complications is lower than with systemic infusions.