This unit outlines the basic steps in planning and carrying out ion-exchange chromatography to separate proteins. Protocols describe both batch adsorption and column chromatography in conjunction with either step- or linear elution gradients. Support protocols describe (1) pilot experiments to determine initial conditions for batch or column chromatography (i.e., pH required for binding, change in pH or salt concentration required for elution, and available capacity of a medium), (2) calculation of the dynamic capacity of an ion-exchange column, (3) methods for producing continuous gradients of pH and salt concentration to elute proteins from ion-exchange columns, (4) regeneration of used ion-exchange media, and (5) storage of ion-exchange media.