Extensive ion exchange equilibrium data is presented for all binary, ternary, and quaternary systems as well as for the five-component system involving the ions H+, Na+, K+, Mg2+, and Ca2+ on the gel-type Amberjet 1200H resin manufactured by Rohm and Hass. Solution concentrations studied are 0.10 mol L-1, 0.20 mol L-1, 0.50 mol L-1, and 1.00 mol L-1. All experiments are conducted with Cl- as the nonexchanging anion at (25.0 ± 0. 1) ° C. This extensive data set is used to test the predictions of a published ion exchange equilibrium model.