This paper describes a case of amusing retroperitoneal teratoma, with a review of the pertinent literature. A 35-year-old female, who had been diagnosed as having a retroperitoneal tumor when she was 3 years old, was seen at the hospital because of severe epigastralgia caused by cholecystolithiasis. She had been refused to extirpate the tumor by various reasons for a long time. Plain roentgenogram of the abdomen revealed a large right lateral abdominal mass containing osseous structure. In computed tomography, the tumor was detected as multiloculated and cystic mass including colorful content as bone and adipose tissue in the cyst, locating anterior to the right kidney. Preoperative diagnosis was benign retroperitoneal teratoma, and she resolved to undergo extirpation of the tumor with cholecystectomy at last. At laparotomy, the tumor was displaced the adjacent organs (right kidney, pancreas head, duodenum and inferior vena cava), and adhered to them besides. Gross findings of the specimen included encapsulated, multiloculated and cystic tumor containing sebaceous like material and yellowish fat including hair and bone in the cyst, with 15.3×10.8×7.9cm in size and 570g in weight. Histologically, the tumor revealed matured benign teratoma of all three germ layers. The patient has been in good health without a sign of recurrence for 2 years and 4 months after the operation.