The aim of the case report is presentation of a rare complication of nephrotic syndrome in form of cerebral sinovenous thrombosis. Ten years old boy, who had been suffering from nephrotic syndrome (biopsy showed minimal changes disease) since he was two, was admitted to the hospital in heavy clinical status with headache, vomiting, disorder of speech and consciousness. Relapse of the nephrotic syndrome began about 2 weeks earlier with heavy proteinuria. Then he was treated by high-dose of steroids (prednisone 40-60 mg/d). Because of changes in the clinical status (aphasia, stereotypic movements without sinus of local brain lesions) the computer tomography was performed. It confirmed only cerebral oedema (near subcortical nuclei). MRI revealed a thrombosis in the left sigmoid, transverse and rectus sinus. Heparin therapy was started and was continued by low molecular weight heparin and oral anticoagulants. Patient required also an intubation for 7 days. Complete renal response was achieved 16 days after admission. Described complicated relapse of nephrotic syndrome didn’t cause any neurological defect in 24-month observation period. Nephrotic syndrome is associated with increased risk of thromboembolic complications. Cerebral sinovenous thrombosis is rare but required increase diagnostic vigilance, because the course is very serious. Early diagnose and intensive therapy enable recovery without any permanent neurological disorders.