Nine Egyptian Baladi cattle heifers 27-35 months of age, were divided into two groups. Group. 1, normal cyclic heifers, received no treatment (control). Group 2 heifers suffering from dysgenesis, never exhibited oestrus, were treated with Norgestomet ear implant +PMSG and PGF2α for induction of oestrus. Blood samples were collected before and after treatment for determination of serum progesterone levels using RIA. In addition, blood samples were collected from both groups for cytogenetical analysis. The data revealed that none of treated heifers showed symptoms of oestrus up to 10 days after treatment, rectal palpation on day 10 after the end of treatment indicated no ovarian cyclical changes (size or structure) which was also confirmed by the basal level of serum concentration (0.19 + 0.02 ng/ml) on the same day. Moreover, cytogenetical analysis of 4 heifers (one had failed in blood culture) indicated a significantly higher (P < 0.01) numerical variations and chromosomal aberrations in autosomes and sex chromosomes of the treated heifers when compared with normal cyclic animals. In conclusion, the results indicated that gonadal development and response to exogenous gonadotrophin were affected by the chromosomal abnormalities in both autosomes and sex X-chromosome in Egyptian Baladi cattle.