We report a case of left renal cell carcinoma extending into vena cava with malignant peritoneal mesothelioma. A 41-year-old man presented to our outpatient clinic with macroscopic hematuria. Upon laparotomy, numerous white nodules were identified on diaphragm and serosa of liver, stomach, small intestine and mesentery. Biopsied specimen showed malignant mesothelioma of peritoneum and renal cell carcinoma of left kidney. He was treated with intraperitoneal cisplatinum and intravenous pirarubicin for mesothelioma, and chemoembolization for renal tumor. After two courses of therapy, he suffered from disseminated intravascular coagulation and died of subarachnoid hemorrhage. Autopsy revealed that intraperitoneal nodules were markedly decreased in number and renal tumor had changed into hemorrhagic necrosis, but tumor thrombus in vena cava had little necrotic change.