The current study aimed to examine the effect of steroid-free bovine follicular fluid (SFBFF) antiserum on ovarian immunohistochemical expression levels of 17β Estradiol in cyclic virgin female rats. After estrus synchronization, 80 adult virgin female Wistar rats (aged 60 days and weighed 156±4.82 g) were randomly assigned into two equal groups (40 females each) and injected intrperitoneally, at late metestrous, with 100 µl of normal saline (control) and 100 µl of SFBFF antiserum (AI-SFBFF group). At each phase of the estrus cycle, 10 females from each group were anesthetized (by injection of 0.4 ml of thiopental sod./ animal), dissected and the ovaries were obtained for determination of immunohistochemical expression density of 17β Estradiol. Ovarian examination of AI-SFBFF group females demonstrated slight increase of estradiol immunohistochemical density at proestrus and mark increase at estrus and metestrus phases. It could be concluded that immunoneutralization of endogenous inhibin by SFBFF antiserum results in high levels of estradiol actions in reproductive organs.