Purified levan is antigenic in man and subcutaneous injection of 1 mg. leads to the production of precipitins and skin sensitivity. Apple amylopectin, maize glycogen, and synthetic polyglucose did not stimulate antibody production in small numbers of individuals injected. Quantitative precipitin studies carried out with several levan preparations employing human antilevan show variations in immunochemical behavior indicating structural differences among levans. Evidence that precipitins formed in response to levan injection are antilevan antibodies was obtained by analysis of specific precipitates formed in the region of antibody excess for ketosugar. Injection of levan giving rise to production of antilevan failed in one individual to give a non-specific anamnestic rise in either antidextran or antiblood group A precipitins. Laminarin, a neutral polysaccharide, was found to give precipitation with normal human sera.