Autologous immune complex nephritis (Heymann nephritis) is mediated by the autoimmune mechanism and can be induced in certain rat strains by immunization with tubular brush border antigen (Fx1A). The present study was undertaken as a tentative approach to prevent this nephritis, by daily intraperitoneal injections of the solubilized Fx1A for the purpose of removing free antibody from the circulation. Administration of solubilized Fx1A was started a week after the immunization for the induction of Heymann nephritis and continued until the animals were sacrificed at 14 weeks. A control group of immunized animals, also observed for 14 weeks, received saline. The injections of the solubilized FX1A decreased the incidence of proteinuria, the amount of immunoglobulin and complement depositions in the glomeruli, and also the titer of antibody against the brush border. It is concluded that the administration of the solubilized antigen exerts a preventative effect on the course of Heymann nephritis, probably due to removing the antibody from the circulation.