Enzyme-linked immunosorbent assay was applied to the determination of the serum IgG antibody contents in rats immunized with the organ-specific autoantigen (S antigen) of the retina.Optimal conditions (i.e. S antigen concentration, serum and conjugate dilutions, enzymatic reaction time) were determined. The assay required only a single serum dilution and was well reproducible. It was very sensitive, allowing the detection of low antibody contents in animals immunized with 1μg of S antigen.The time course of the antibody response and its variations according to the dose and the species of the immunizing S antigen were considered.