A total of 777 samples which include (180 samples of cervical secretions, uterine biopsy, eight genital tracts of slaughtered cows, 21 aborted foeti, 40 foetal membranes, 162 semen samples and 33i preputial washings) were used in the study. All these samples were cultured bacteriologicaly for isolation of Campylobacter microorganisms. Six virgin heifers were also used to reproduce the disease and to elucidate the pathogenicity of the organism. Based on the morphological, cultural and biochemical characters of 67 isolates of Campylobacter organisms three different trains were identified for the first time in Egypt. Strain No. l and, train No.2 proved to be mutant strains of Campylobacter. fetus subsp. fetus. Strain No.3 Campylobacter sputorum subsp. bubulus was found to be non- pathogenic. These findings were discussed in relation to the problem of infertility.