Summary A method is described which allows the isolation of antigenically pure samples of the three immune globulins: γss (=7 S γ), γ1M (=19 S γ) and γ1A (=β2A), starting from individual serum samples. The γss-globulin is obtained by chromatography on diethylaminoethyl-cellulose. Preparative ultracentrifugation in a sucrose density gradient is used to obtain the γ1M-globulin from a euglobulin precipitate. The γ1A-globulin is isolated from the remaining pseudoglobulin solution, by means of a modified fractionation procedure using precipitation with zine sulfate, preparative electrophoresis and salting out with ammonium sulfate, in the order indicated. The purity and recovery rates of the three immune globulin fractions are assessed, and their value as representatives of the corresponding immune globulin groups of native serum is critically discussed.