Seventy-one Holstein-Friesian divided into five groups (Three groups of females and two groups of males) were investigated cytogenctically to identify and score any chromosomal aberration which may be encountered. The female groups were repeat breeder group (25 animals), and freemartin group (4 animals) in which the females are heifers aged from 3 to 4 years and the third group was pregnant heifers (25 animals control) aged 2 to 2.5 years. The male groups were young males aged from 12 to 18 month (8 animals with unilateral testicular orchidy) and breeding bulls (8 control animals) aged 3 years. Blood samples (vere collected from these groups for cytogenetical analysis. The highest percentage was detected for the total structural aberrations (25 68%) which are significantly higher than that observed for total numerical aberrations (11.84%)  in the repeat breeders group. The freemartins had equal numbers of metaphases with xx and xy, and 35 were found to have numbered (20 and 5%) of structural and numerical variations,  the percentage of total chromosomal aberrations was 25%. The total structural aberrations in the © affected male group (26.75%) were significantly higher than numerical variations (11.0%). ‘The total numerical and structural aberrations, the percentage in the affected male group (37.75%) is significantly higher than that found in the normal :control group (16.3%)