Twenty patients with the diagnosis of pheochromocytoma were studied from January 1990 to January 1998. Nineteen patients had a pathologic investigation performed. The mean age of patients was 49 +/- 16 years (range: 24-71 years), 8 males and 12 females. Nine cases corresponded to adrenal and eleven to extra-adrenal (paragangliomas) pheochromocytomas. The anatomic location was similar in both adrenal glands and for paragangliomas the cervical location predominated. The most consistent clinical finding in our patients was maintained arterial hypertension, followed by headache, palpitations and flushing. Biochemically, an increase in urine catecholamine levels or their metabolites was found in 82.2%. The clonidine test was very useful, particularly for cases where biochemical results were discrepant. CT, NMR and gammagraphy with 123I-MIBG have a high sensitivity for locating pheochromocytomas. NMR and gammagraphy with 111In-pentetreotide located cases in which CT or 123I-MIBG were negative. Preoperative treatment with adrenergic alpha-blockers allowed to surgery with no arterial tension complications. Only one patient with multiple abdominal paragangliomas relapsed. No differences regarding clinical manifestations, biochemical parameters or imaging studies were found between pheochromocytomas and paragangliomas, except their location.