Pheochromocytoma contains and may synthesize a large number of peptides such as opioids (Leu-, Met-enkephalin), VIP, gastrin, calcitonin gene related peptide (CGRP), somatostatin, and adrenocorticotrophic hormone (ACTH). Also, circulating level of these peptides may be elevated. Although the precise contribution of these peptides secretion to the clinical features are largely unknown, it can be suggested that specific endocrine system could be involved in ectopic hormone production by pheochromocytoma. Indeed, it has occasionally been reported that pheochromocytoma is associated with Cushings syndrome resulting from excess ACTH production. As there are already many excellent reviews of this area, the discussion that follows will mainly focus on our data, including 1.Opioids, 2.Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP), 3.Natriuretic peptides (NPs), 4.Leptin, 5.Endothelin 6. Angiotensin II receptor, 8. Chromogranin A and Catestatin.