Antigenic substances showing common reaction to B. megaterium TU, and other substances showing different antigenicity were contained in the culture fluid of B. anthracis. Acid precipitated fraction contained protein and it showed reactivity as an precipitinogen. This is a different antigenicity from B. megaterium. The fraction which did not precipitate with acid consisted mainly of polysaccharide. It demonstrated the existence of antigenic substance having a common reaction to B. megaterium.