The reproductive form of Haemophilic infection caused by a microorganism Histophilus somni (Haemophilus somnus) is in our conditions practically unknown and undiscovered disease of cow reproductive organs. The aim of this work was based on experimental work to provide a comprehensive view on the pathohistological and submicroscopic changes in the uterus of 60 cows, serological positive, crossbreeds Slovenské strakaté x Holstein, aged 3.5 – 4.5 years, serological positive, which were up to 90 days after the parturition sterile. After the hormonal control of the oestrus cycle (PGF2α-Oestrophan SPOFA) the cows were inseminated and the non-gravid cows later killed. The reproductive organs of killed animals were pathologically – anatomically dissected with following histological and sub-microscopic study of uterus and cervix tissue. At the beginning of the experiment no clinical changes of the reproductive organs of group 1 animals with the titer of antibodies 1:25-100 were diagnosed and in group 3 with the titer 1:25. At an examination before killing were examined endometritis (EM) of grade II. and vaginitis with vestibulitis in these groups. At the rest of animals appeared in every level of the titer of antibodies of EM II. and EM III. EM I. were not clinically diagnosed. Dissecting examination determined EM catarrhalis and cervicis catarrhalis in all groups. The histological examination pointed to EM catarrhalis chronica, EM interstitialis chronica, EM fibrousis and cervicis catarrhalis chronica. The leucocytes gained from a uterus lavage were in a comparison with stroma leucocytes mostly polynuclear (neutrophils) and in smaller amount small forms of lymfocytes. At long-term sterility of cows, because of possible H. somnus infection, we regard as priority the serodiagnostics at which is taken into consideration any level of the titer of antibodies.