We report seven cases of intravenous leiomyomatosis. Growth beyond the uterus occurred in two of the seven cases in the broad ligament. One 21-year-old patient is one of the youngest reported cases in the literature. Five patients had total abdominal hysterectomy with removal of the adnexa and two patients underwent myomectomy. One of the myomectomy cases had abdominal hysterectomy and bilateral salpingo-oophorectomy one year later due to recurrence. The other one was disease free six months after the operation. Vessel walls harboring intravascular tumor were investigated immunohistochemically for Factor VIII, CD 34, estrogen and progesterone receptors with the hope of making the histogenesis of intravenous leiomyomatosis clear. Immunohistochemical analyses of estrogen receptors, progesterone receptors, vimentin, desmin, smooth muscle actin, CD 10 and h-caldesmon were performed on intravascular tumor cells. Endothelial and subendothelial cells expressed none to scant, very weak progesterone and estrogen receptor positivity. Intravascular tumor cells showed weak (10%) to strong (70%) progesterone receptor positivity and weak (10%) to strong (60%) estrogen receptor positivity. These results do not support the hypothesis of a vessel wall origin for intravenous leiomyomatosis.