Pheochromocytoma can cause several paraneoplastic syndromes. We report a patient with pheochromocytoma who exhibited pyrexia and marked inflammatory signs along with an elevated serum interleukin-6 (IL-6) level. All of these abnormalities disappeared and serum IL-6 became undetectable by removal of the tumor. In addition, immunohistochemical analysis revealed the presence of IL-6 in the tumor cells. It is suggested that pyrexia and the elevation of acute phase proteins can be a paraneoplastic syndrome with pheochromocytoma, and that the elaboration of IL-6 from pheochromocytoma may play an important role in the development of the syndrome.