Leiomyosarcoma of the renal vein is a rare neoplasm occurring more commonly in women. On sectional imaging it is difficult to differentiate from other primary retroperitoneal tumors. Here is a case report of a right renal vein leiomyosarcoma in a 40-year-old man. The ultrasound findings are described and the magnetic resonance imaging, computed tomography, and angiographic findings are illustrated and correlated with the pathologic findings.