Thrombolytic therapy usually used for thrombosis in the adult has been administered as a therapeutic regiment in pediatric patients (parental consent was sought prior to the treatment with rt-PA). We report our experience with rt-PA in 17 children and adolescents suffering from arterial (n = 4) or venous thrombosis (n = 13) due to local rhabdomyosarcoma, acute lymphoblastic leukemia, chronic myeloblastosis, sickle cell anaemia, parenteral nutritrition, haemolytic uremic syndrome, central arterial and venous catheters and septicemia Thrombotic diseases have been diagnosed by Doppler ultrasound, computed tomography, angiography and phlebography. Rt-PA therapy was started immediately after diagnostic procedures had been performed. Rt-PA dose varied from 0.2 mg as a single dose to 0.8 mg/kg bw/d over a three day period in children local thrombolysis was performed. In patients requiring systemic thrombolytic therapy rt-PA was administered from 0.8 mg/kg bw/d in three days to 2.0 mg/kg bw/d over a whole period of three weeks in both groups during thrombolysis low dose heparin was added. When rt-PA infusion was terminated heparin (70 IU - 400 IU/kg bw/d) was administered for 7 to 14 days in order to prevent reocclusion. Later prophylaxis with coumarine derivatives in venous thrombosis and antiplatelet agents in arterial occlusive diseases was performed. In no patient did we see a decrease of fibrinogen and plasminogen during rt-PA therapy. No severe side effects, for example cerebral intraventricular bleedings in neonates, occured. Complete reperfusion was seen in 13 patients, partial reperfusion in two children. In one adolescent thrombolytic therapy was started three weeks after the initial thrombotic event: without success. In an eight month old girl we had to stop rt-PA infusion due to a bleeding out of a recent central vein puncture. We believe thrombolytic therapy with rt-PA in childhood to be a useful therapeutic regimen to prevent severe post-thrombotic syndrome, which also occurs in pediatric patients.