A 35-year-old man presented with a 17-month history of abdominal distension and left upper quadrant pain. He had no episodes suggesting the presence of hypertension. Hormonal studies were insignificant. Imaging studies demonstrated a bulky tumor with cyst formation measuring 22 cm. Preoperative differential diagnoses included an adrenal tumor, extra-adrenal retroperitoneal tumor and pancreatic mucinous tumor. Intraoperatively, no abnormality was observed in the pancreas. A tight adhesion of the tumor to the left kidney necessitated an en bloc resection of the tumor with the left kidney. The resected specimen, 22 x 20 x 8 cm, weighed 5,050 g. Pathologically, the tumor was ganglioneuroma originating from the left adrenal gland. Convalescence was uneventful, and abdominal symptoms disappeared. The patient has been doing well without evidence of recurrece 48 months after the operation.