SummaryImmediate, type I, prick test reactions in man to purified fractions ofCandida albicansgroup A were mediated by different classes of antibody. The allergens were the cell‐wall polysaccharide, mannan, and a ‘purified’ cytoplasmic protein fraction, free of mannan, prepared by passage through Sepharose‐concanavalin‐A. Passive transfer tests in the monkey gave immediate reactions, (1) to the purified, cytoplasmic, protein mediated by heat‐labile long‐term sensitizing antibody, and (2) to the polysaccharide, mannan, mediated by heat‐stable short‐term sen