A case of fibrosarcoma of the kidney extending into the inferior vena cava with intraoperative development of massive neoplastic pulmonary emboli is reported. A 38-year-old man was admitted to our hospital because of right renal tumor with gross hematuria, right flank pain and abdominal tumor. Inferior venacavograms and computerized tomography demonstrated almost total occlusion of the abdominal part of the vena cava by tumor thrombi. No signs of inferior vena caval involvement were present. Intraoperative pulmonary neoplastic emboli suddenly occurred after right nephrectomy was performed. Immediately, pulmonary thrombectomy was performed with extra-corporeal circulation. Postoperatively, pulse, blood pressure and ventilation were stable, but the patient remained unconscious and neurologic signs gradually deteriorated. Computerized tomography of the brain showed diffuse brain edema and infarctions. The patient died of cardiopulmonary insufficiency with multiple pulmonary metastasis 8 months postoperatively. We emphasize the risk of fragmentation and migration of the tumor thrombi during surgical treatment of neoplasm of the kidney invading the inferior vena cava.