A case of retroperitoneal liposarcoma is reported. A 42-year-old woman was admitted to our hospital with the complaint of a palpable mass in her left abdomen. Intravenous pyelography, barium enema and an ultrasonogram revealed a huge left abdominal tumor. At operation, a huge yellow-brownish tumor found in the retroperitoneal space, was completely removed. The tumor was 32 x 24 x 12 cm and weighed 4,075 g. Histologically, it was a myxoid liposarcoma. Three courses of adjuvant chemotherapy (cis-platin) were administered. The postoperative course was uneventful and the patient has been free of disease for 16 months.