Epinephrine (adrenaline), norepinephrine (noradrenaline) together with dopamine constitute the group of catecholamines, which play an important role as hormones and neurotransmitters. After they have exerted their effects, the catecholamines are broken down via intermediate products (metanephrine, normetanephrine, 3- methoxytyramine respectively) and finally excreted in urine. Diseases which are associated with altered levels of catecholamines include hypertonia,degenerative heart diseases, and catecholamine-producing tumors (pheochromocytoma,neuroblastoma, ganglioneuroma). Of these, pheochromocytoma has the greatest significance. Around 10% of all pheochromocytomas show malignant growth and an unidentified pheochromocytoma poses a serious health risk to the patient. The determination of catecholamines is therefore essential in patients with suspected pheochromocytoma.