Zeolite A and calcium phosphate modified Zeolite A have been shown to be a new effective packing material in ion exchange chromatography for the purification of immunoglobulin G (IgG) from binary mixtures and mouse ascites fluid. This study was to determine the effectiveness of purifying IgG using Zeolite X and dealuminated Zeolite X with twice the pore size of Zeolite A. Binary mixtures (IgG-albumin and IgG-transferrin) and a mouse ascites fluid were purified in Zeolite X (in Na+, K+, or NH4+ form) chromatographic columns and with dealuminated Zeolite X under a variety of operational conditions. The biological activity of the purified IgG from the mouse ascites fluid was confirmed by ELISA. The characteristics of zeolites in the present study suggest that functional groups of a protein displace the cations of zeolites near the crystal surfaces and create a different strength of affinity. The study demonstrated that Zeolite X and dealuminated Zeolite X are also promising new packing materials for the purification of IgG from biological materials.