Аннотация:Synaptonemal complexes of spermatocytes I obtained from C57BL/6j male mice treated with inactivated bacterial vaccines were spread over the hypotonic phase and then were investigated using light microscope. The slides of synaptonemal complexes of mice treated with cyclophosphamide were used as positive control. It is shown possible in principle to reveal synaptonemal complex abnormalities by means of light microscopy. These abnormalities were not more frequent in vaccinated animals than in intact ones. Cyclophosphamide at doses of 100-200 mg/kg induced synaptonemal complex damage practically in 100% of cells 96 hours after the injection.