The authors studied the appearance and behavior of complement-fixing anti-ROS antibodies in the sera of GrCh rabbits following one or two intracutaneous injections of retinal antigens emulsified in Freund's complete adjuvant (KFA). Fourteen different antigenic preparations from heterologous, homologous, and autologous retinal components incorporated in KFA were tested and compared. Apart from the supernatant of a centrifuged homogenized preparation of homologous retina, all immunogens generally induced anti-ROS antibodies. The antibody titers (reciprocal values) reached a maximum 4 to 8 weeks post injection, at only low levels. The changes in antibody concentrations showed some relationship to the quality and dose of the immunogens. Anamnestic effects following reinjection reached maximum values within as little as 5 to 14 days. Animals not developing chorioretinitic lesions showed higher antibody titers more frequently than rabbits with clinically confirmed disease. Provided there is sufficient relevance of the humoral reactions observed, the complement-fixing antibodies we found in our experiments are more likely to have protective than pathogenic functions.