Evidence is here given that polysaccharides can be rendered antigenic by haptogenic adsorption upon a colloid carrier. The polysaccharides studied were those of B. anthracis, the meningococcus, Streptococcus viridans (Bargen), B. proteus, S. morgani, B. dysenteriae, both the Shiga and Hiss types, and the pneumococci. With the polysaccharide of Type III pneumococci, we have been unable in 6 weeks to produce any detectable protective antibodies, but we were able to produce anticarbohydrate antibodies. All the bacterial carbohydrates were non-antigenic alone when used in the doses indicated, though containing some nitrogen. Dextran, which was free from nitrogen was also rendered antigenic by the adsorption method.