Objective To analyze the clinical characteristics of nonfunctioning pheochromocytoma, and to evaluate the efficacy of 131I-metaiodobenzylguanidine (MIBG) scan in the diagnosis and perioperative treatment of nonfunctioning pheochromocy- toma. Methods The clinical data of 14 patients with nonfunctioning pheochromocytoma were analyzed retrospectively. Plasma free corticoid, renin, aldosterone, and urine catecholamines levels were estimated. B-mode ultrasonography, computed tomo- graphy scan, thoracic X-ray and 131I-MIBG were used. Results All patients with nonfunctioning pheochromocytoma had no hypertension and the tumors were found inciden- tally. The 24 hours urine catecholamines levels in 80% (8/10) patients were normal. The positive rate of 131I-MIBG was 80% (8/10) and the specificity was 100%. All patients underwent surgical operation of tumor resection. No preoperative volume expansion was given to all patients. All tumors were resected completely, and no death accident happened. There was no recurrence and metastasis after operation by long-term follow-up. Conclusion 131I-MIBG scan is the first choice technique for the diagnosis of nonfunctioning pheochromocytoma. Blood volume expansion is unnecessary before resection of pheochromocytoma.no recurrence and metastasis}) Objective To analyze the clinical characteristics of nonfunctioning pheochromocytoma, and to evaluate the efficacy of 131I-metaiodobenzylguanidine (MIBG) scan in the diagnosis and perioperative treatment of nonfunctioning pheochromocytoma. Methods The clinical data of 14 patients with nonfunctioning pheochromocytoma were analyzed retrospectively. Plasma B-mode ultrasonography, computed tomography, thoracic X-ray and 131I-MIBG were used. Results All patients with nonfunctioning pheochromocytoma had no hypertension and the tumors were found The positive rate of 131I-MIBG was 80% (8/10) and the specificity was 100%. All patients underwent surgical operation of No preoperative volume expansion was given to all patients. All tumors were resected completely, and no death accident happened. Th ere was no recurrence and metastasis after operation by long-term follow-up. Conclusion 131I-MIBG scan is the first choice technique for the diagnosis of nonfunctioning pheochromocytoma. Blood volume expansion is unnecessary before resection of pheochromocytoma. no recurrence and metastasis})