Reversed micellar extraction was applied for the fractionation of IgG fragments. With isooctane solution containing 50 mM AOT, Fab, Fc and IgG were extracted to the micellar phase. Each protein had an optimum pH range in the extraction. Fab and Fc were separated from the mixture at pH 7.0, with Fab being extracted to the micellar phase and Fc remaining in the aqueous phase. Extracted Fab fragments were recovered by bringing them into contact with 6M guanidine/HCl followed by dilution with PBS. Fab and Fc fragments were separated and recovered by reversed micellar extraction from IgG lysate digested with papain. Since the procedure is simple and rapid compared with column chromatography, mass preparation of the fragments can be expected by this method.