In the present study, controlled burns of 1 testis have induced the formation of testis-specific antibodies in Hartley guinea pigs. The antibodies reacted with autologous as well as homologous testicular extracts. In addition, pathological changes have been noted in the germinal components of the contralateral testis, which were similar to those observed after the induction of experimental allergic orchitis by active immunization with testicular tissue. Results of the study indicate that thermal injury to guinea pig testes can induce an autoimmune response similar to that observed after immunization with autologous or homologous testicular tissue. The antibodies formed were organ-and species-specific against a testicular antigen. Thermal injury may be associated with autoimmunization of the host by the injured organ.