A case of intravenous leiomyomatosis with extention into the right ventricle is described. A tumor in the inferior vena cava was detected three years after a subtotal hysterectomy had been performed for a myomatous uterus but was misdiagnosed as a thrombus. The tumor enlarged and intruded into the right ventricle for which she underwent surgery. The correct diagnosis was made during the surgery, therefore a two-stage resection was planned. Surgical resection is the best treatment for intracardiac extention of intravenous leiomyoma. We recommend iliac venotomy to remove the ilio-caval portion of the tumor in both stages of operations. (C) 2004 by The Society of Thoracic Surgeons.