Five virgin buffalo heifers were used in the study. Animals were inseminated with artificially infected semen. The used campylobacter organisms were previously isolated from an aborted buffalo foetus and the organism was classified as a mutant strain of Campylobacter fetus subssp. fetus. The animals showed oestrus once or twice after infection. In addition, vaginitis, cervicitis and endometritis were observed in most cases, three heifers were found pregnant. The organism was successfully re-isolated from four animals. The microorganism was re-isolated from vagina of four animals, the cervix of three, the uteri of three and from the oviducts of one. Re-isolation failed from the fifth (No.3) and its pregnancy was apparently normal. The re-isolated microorganism was similar culturally, morphologically and biochemically to the original stain used in the experiment. The microorganism was also re-isolated from the bull (previously free from campylobacter) after four weeks from its introduction to the infected animals and after three weeks from its service to an infected animal. It is believed that the mutant strain of Campylobacter fetus. Is the dominant type in Egypt causing infertility and further work is needed to elucidate its role in the problem of infertility in Egypt.