In an experiment of vaccination against caprine arthritis encephalitis virus (CAEV), the antibody response in three groups of young goats was followed by AGIDT, ELISA, seroneutralization, western blot. Goats of group I, inoculated with inactivated virus mixed with adjuvant, showed a few weeks after vaccination a high antibody response, clearly enhanced after infectious intraarticular challenge. These antibodies did not protect against arthritis, which appeared more severe in this group. In the other groups (group II, control adjuvant, with the weakest clinical expression, group III, control tissue culture medium), the levels of circulating antibodies appeared much lower. No neutralizing antibodies could be detected during the whole experiment. A western blot analysis revealed mainly in group I a high antibody response against gp 135 antigen. The important immune reaction might be involved in enhancement of viral infectivity in this group.