Ion exchange chromatography is a chromatography process that separates ions and polar molecules based on their affinity to the ion exchanger. Ion exchange chromatography is probably the most powerful and classic type of liquid chromatography. It can also used for almost all kinds of charged molecule including large proteins, small nucleotides and amino acids. This topic includes background, theory, application and instrumentation. It is the most effective method for water purification. Inorganic ions also can be separated by ion exchange chromatography. The present review summarizes the instrumentation, validation method and application of ion exchange chromatography. Keywords; Chromatography, Anions, Cations, Ion exchange resins