The results of fibrinolytic therapy with urokinase were evaluated in 26 neonates with catheter related central venous thrombosis. Complete thrombolysis could be achieved in 13 patients (50%), partial thrombolysis in 3 patients (12%). No effect was seen in 10 patients (38%). Therapy success was influenced by age, size and location of the thrombus. Coincidence of infection occurred in 16 patients (62%). Mild hemorrhagic complications were seen in 2 patients (8%), no other significant side effects were observed. Nine patients with residual thrombosis were treated with oral anticoagulants following urokinase resulting in resolution of the thrombus in 6 patients within 3 months (67%). The incidence of asymptomatic recurrent thrombosis was high (28%). Urokinase might be an effective and safe treatment for central venous thrombosis in neonates. Prophylactic antibiotic therapy during the infusion of urokinase and long-term treatment with oral anticoagulants after thrombosis are advisable. Early detection of thrombosis might enhance the success rate of fibrinolytic therapy. Therefore, we strongly recommend routine echocardiographic screening of central venous catheters.