Chronic candidosis was established in rabbits by the injection I.V. of 2×106 cells of C. albicans. The rabbits were assayed every week for 14 weeks for the appearance of Candida antigen and anticandida antibodies in serum and other body fluids. Tests were carried out in double diffusion plates; antigen against hyperimmune rabbit sera and antibody against Candida cell sap antigen preparation. A sensitive specific passive hemagglutination procedure was also developed which used chromate treated cells. In rabbits with chronic candidosis not treated with cyclophosphamide antigen was detected in 4x concentrated serum between the fifth and sixth week. At about the same time antibodies were demonstrable and theafter antigen was no longer detected. Maximum antibody titer occurred between the eight to 10th week and disappeared thereafter. If cyclophosphamide 30 mg/kg was given at this point, anticandida antibodies reappeared in high titers, persisted for three to four weeks and then disappeared. At autopsy no evidence of candidosis was present. If rabbits were pretreated with cyclophosphamide 60 mg/kg for one week before inoculation and given the drug weekly thereafter no antibody was detectable but antigen and antibody were present in body fluids (not serum) at post mortem.