Over a period of 22 years, 447 children with nephrotic syndrome (NS) have been retrospectively studied for clinically apparent thromboembolic complications (TEC). The incidence of TEC is 2% (9/447); 16 clinically apparent TEC were registered in 9 children. The incidence of TEC was 1.5% among patients with steroid-sensitive NS and 3.8% among those with steroid-resistant NS. TEC were predominantly venous (81% venous vs. 19% arterial). The most commonly affected vessels were deep leg veins, followed by inferior vena cava (IVC). Rare locations of TEC were also observe--superior vena cava (SVC), mesenteric artery, IVC, and hepatic veins with the development of Budd-Chiari syndrome. Depending on the location of the TEC, imaging techniques used were: X-ray, computed tomography, and Doppler sonography. The major iatrogenic risk factor was furosemide, administered to 7 of the 9 children with TEC. In some patients additional predisposing factors were infections, dehydration, trauma, venepuncture, and immobilization. Treatment with heparin was followed by oral anticoagulation. Fibrinolytic therapy was effective in 3 of 4 patients. No new TEC occurred under oral anticoagulant prophylaxis. The outcome was a full recovery in 6 patients and a partial recovery in 1 patient. Two children died--1 with SVC thrombosis and the other with recurrent TEC affecting cerebral vessels. Although rare, TEC are among the most serious life-threatening complications in children with NS and require intensive care.