This is a case report of retroperitoneal leiomyosarcoma in a 61-year-old woman. She presented with a chief complaint of back pain. Computed tomography showed a left huge retroperitoneal tumor. The tumor was removed with left nephrectomy and left hemi-colectomy. Histological examination demonstrated leiomyosarcoma 26 x 20 x 16 cm in diameter and, 3.84 kg in weight. She died of local recurrence causing ileus 2 months after the surgery. Fifty-four cases of retroperitoneal leiomyosarcoma including the present case in the Japanese literature are reviewed.