Epinephrine (E), norepinephrine (NE), and dopamine (DA) belong to a class of compounds known as catecholamines. A number of physical and chemical properties of E and NE, together with analytical techniques used to measure these amines and their metabolites, are reviewed. E was originally isolated from bovine adrenal glands; however, E and related compounds are now synthesized commercially from the starting material, catechol. The biosynthesis, storage, release, and the termination of action of catecholamines by re‐uptake into the presynaptic neuron that released the amine, plus mechanisms involved in regulating levels of amines in the nerve terminals, are reviewed. By virtue of functional and molecular biology studies, at least 15 subtypes of catecholamine receptors have been identified. In most cases, these physically distinct subtypes each have important second messengers and pharmacological consequences that are summarized. Catecholamines and related compounds exhibit a wide diversity of physiological functions, and thus are involved therapeutically in a wide range of uses both in the peripheral and central nervous system.