Tetraethylammonium (TEA) or (Et4N+) is a quaternary ammonium cation consisting of four ethyl groups attached to a central nitrogen atom, and is positively charged. It must exist in association with a counter-ion, and is most commonly found in simple salts such as tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide and tetraethylammonium hydroxide. Tetraethylammonium salts are used in chemical synthesis, have briefly been used in clinical applications, and are widely employed in pharmacological research. The identity of the anion associated with the tetraethylammonium cation frequently has little or no bearing on a particular chemical or biological type of action, but this is not invariably so.