SUMMARYThe absence of Group D antigen from the cell walls and protoplasts of Group D streptococci leads to the conclusion that this antigen is located between the protoplast membrane and the cell wall. The Group N antigen was likewise not present in cell walls of Group N streptococci and probably has a similar location to the Group D antigen. The Group Q strains examined possessed the Group D antigen in the cell contents although these strains did not physiologically correspond to any established Group D species. The antigen upon which Group Q is based is a cell-wall antigen.