Experimental autoimmune oophoritis (EAOO) induced in female Lewis rats by a single injection of isologous ovary in complete Freund's adjuvant (CFA) and concentrated pertussis vaccine resulted in a multifocal accumulation of mononuclear cells in ovaries and complete loss of fertility after 17-28 days. The time course of appearance of anti-ovary antibodies and their serum titers showed a good correlation with the reduction of litter size. Furthermore, the infertility also could be induced by passive immunization of rats with adsorbed anti-ovary serum. The contraceptive effect of the antibody does not result in permanent sterility. Besides lymphoid cell infiltrations, the most prominent histological alterations in ovaries of experimental rats were characterized by a significant increase in the number of atretic preantral and antral follicles and a decrease in the number of growing follicles of all sizes and corpora lutea. It is presumed that both the direct effect of anti-ovary antibodies and disturbance in ovarian morphology can lead to a reduction of litter size and appearance of infertile cycles in rats with oophoritis.