The ovary of a laying hen contains follicles in the rapid growth phase which have advanced from a pool of follicles in the resting stage of about ٦-٨ mm in diameter. Little is known about mechanisms regulating follicular transformation from the resting stage to the rapid growth phase. One potential regulator of this transformation may be Follicle Stimulating Hormone (FSH). In addition, there are accumulating results indicating that a negative relationship between inhibin and FSH may be existed.