Extrarenal angiomyolipoma is an uncommon disease entity and is rare in the retroperitoneum. We report a case of giant extrarenal retroperitoneal angiomyolipoma mimicking liposarcoma. A 35-year-old woman presented with a history of increased abdominal circumference and urinary frequency. Abdominal computerized tomography demonstrated a 24 x 21 x 16 cm retroperitoneal fatty tumor displacing the right kidney to the left upper quadrant of the abdomen. At laparotomy, the tumor was widely excised and the right kidney was successfully preserved. Final histologic examination identified the tumor as an angiomyolipoma. At 4-month postoperative follow-up, no evidence of tumor recurrence was found and the right kidney was fully functional.