The authors report on a boy with typical course of recent nephrotic syndrome, who developed massive thrombosis involving the iliac inferior holden veins during the standard therapy with corticosteroid. The first sign of this complication was pulmonary embolism. Thrombosis was treated by surgery, during which 3 large thrombi from veins were removed. The patient developed recurrent thrombosis occurring at the previous sites in the later stage and he died 23 days after the first sign of thromboembolic complication. Autopsy showed only minimal glomerular changes. The cause of the death was massive pulmonary embolisation. The aethiopathogenesis of the complication and preventive approach in children with nephrotic syndrome are discussed.