The present work was carried out to study the effect of zeranol on the seminal glands of 39 male fat-tailed lambs about 8 monthes old. The examined animals were classified into three groups. The group 1, was considered as control, while group II and III, were implanted subcutaneously in the backside of the ear with 3 doses, each of 12 mg, zeranol at 40-days intervals; Group I and II, were fed on concentrates mixture containing 70.45% starch and 14.42 (high) digestable protein, while that of group III, containing 70.44% starch and 7.92% (low) digestable protein. The seminal gland of zeranol implanted lambs showed an obvious decrease in weight, and glandular cell hight and their nuclear diameter. In addition, zeranol induced a marked morpholoical signs of decreased cytoplasmic basophilia, lipid content and PAS-positive materials.