Leimyosarcoma of the inferior vena cava is a rare disorder and may present with symptoms of obstruction of the normal flow of blood. We report a case of leiomyosarcoma of the inferior vena cava in 55-year-old female patient. The tumor was discovered incidentally by ultrasonography of the abdomen which was performed to evaluate epigastric pain and indigestion. Further radiological studies including CT and inferior vena cavography confirmed the presence of a 5cm sized mass in the inferior vena cava . The microscopic examination of a specimen obtained by a catheter from inferior vena cava mass revealed malignant mesenchymal tumor. The tumor was completely resected with reconstruction of the inferior vena cava and left renal vein. The diagnosis of leiomyosarcoma was made by micoscopic and immunohistochemical findings of the resected tumor.(Korean J Med 60:92-96, 2001)