An antigen composed of glycerophosphate and glucose has been isolated from the cell walls of a strain of Staphylococcus albus. The antigen reacted with homologous and heterologous S. albus antisera. Similar material was isolated from the cell walls of three other S. albus strains. The antigen did not react with S. aureus antiserum nor with normal human or rabbit serum. The antigen appeared to have a backbone structure of glycerophosphate with appended monoglucoside units. The antigenic determinant was shown to be glucose in alpha linkage.