As evidenced by precipitin analysis with pooled human gamma globulin, at least 12 distinct antigens were produced in cultures by one strain of Group A streptococcus (C203S). It was suggested on this basis, that these antigens were produced in vivo during human infections. By the combined use of continuous flow electrophoresis on paper curtains, and column chromatography with calcium phosphate gels, five of these have been isolated in a probable high state of purity. One of the components was obtained from culture filtrates of a Group C streptococcal strain. Three of the purified antigens have been tentatively identified as streptolysin "O", diphosphopyridinenucleotidase, and proteinase precursor. The latter could be very readily crystallized, and appears "identical" with that described by Elliott. The DPNase was of extremely high potency, 1 mg. being capable of destroying 12.6 gm. of DPN in 7(1/2) minutes at 37 degrees C. The identity of the other two components is uncertain as yet. They are distinct from each other and the above products immunologically, and are not related to the "C" carbohydrate. The applicability of these methods for the analysis of infectious diseases generally was discussed.