Protein A/G Sepharose is prepared by covalently coupling recombinant Protein A/G (contains five Ig-binding regions of protein A and three Ig-binding regions of protein G, Cat. 6502) to 6% cross-linked sepharose beads. The coupling was optimized to give a high binding capacity for IgG. The capacity of IgG binding could be greater than 10 mg of human IgG per ml of wet gel.