Catalytic autoimmune antibodies from the sera of lupus patients were purified using histidyl-aminohexyl-Sepharose gel and compared with the antibodies purified with protein A and protein G affinity chromatography. The IgG preparations from the histidine affinity column had a much higher catalytic activity in hydrolyzing the peptide substrate Pro-Phe-Arg-methyl-coumarinamide compared to the antibodies obtained by the conventional protein A/G method. This preservation of catalytic activity is attributed to the gentle buffer conditions used in the histidine ligand method that allowed the integrity of three-dimensional structure of purified catalytic antibodies. Thus, histidine affinity offer a superior method for isolating autoimmune catalytic antibodies.