Twenty patients, 16 males and 4 females, aged 11-76 yr, were treated for a metastatic pheochromocytoma at our institution between 1985 and 1990. A neurofibromatosis was associated in 4. Thirteen patients had a unilateral adrenal tumor, 3 had an extraadrenal retroperitoneal tumor, 2 had a bilateral adrenal pheochromocytoma, one had a unilateral tumor with a contralateral medullary hyperplasia and one an adrenal and an extraadrenal pheochromocytoma. Metastases occurred in all patients, at presentation in 11, 10 to 30 months later in 7, and 9 and 28 yr later, respectively in two. Histology did not afford conclusive evidence for malignancy. Catecholamine hyperproduction was present in all, predominantly affecting norepinephrine. Neuron Specific Enolase level was elevated in 11, Neuro-Peptide Y level in 9 and procalcitonin level in 11/18. High dopamine, methoxytyramine and homovanillic acid excretion levels seemed to correlate with large tumors or terminal stage. MIBG uptake was found in 16 after a diagnostic dose and in 1 only after a therapeutic dose. Surgery was performed on primary tumor in 18 and on distant metastase in 10. Iodine-131 MIBG therapy was performed in 11, among whom 9 were evaluable. Cumulative activity ranged from 100 to 711 mCi, in 1 to 6 courses. Symptomatic improvement occurred in 5 patients, stabilization was observed in 3 and tumor partial response in two, which lasted for 28 and 9 months, respectively terminating in a rapidly progressing disease with bone marrow involvement. Moderate myelosuppression occurred in 4 patients. Chemotherapy gave no response in 7 evaluable patients. Fourteen patients died with a median survival of 16 months from diagnosis of metastases (range 3-60). Response to therapy was poor and warrants further cooperative trials.