This study evaluated the effect of ANTORIN R-10(pFSH), a commercially available follicle stimulating hormone on ovarian morphology, on follicular development and serum estradiol levels in rats. Immature female Wistar S/T rats(27 day old; 80-100 g B.wt) maintained under controlled environmental conditions($22{\pm}2^{\circ}C$; 50% humidity; 12 h light/12 h dark cycle) with free access to standard laboratory feed and tap water were utilized. Animals were allowed to acclimatize to the new environment for at least 2 weeks before being included in the experiment. Rats were randomly allotted to 5 groups(Control, SL 0.1AU, SH 0.2AU, TL 0.1AU and TH 0.2AU). ANTORIN R-10 was subcutaneously injected twice daily for 3 days. Twenty hours after hormone treatment, blood was collected to estimate the serum estradiol $17-\beta$ concentration. Immediately, all rats were sacrificed and the ovarian morphology, ovary weight and number of follicles were recorded. Ovaries were fixed for histomorphological examination. Higher standard and treatment groups were significantly increased on ovary weight and the number of follicles more than 1mm compared with lower standard and treatment. However, no difference revealed between standard and treatment groups. ANTORIN R-10 was similar effects of follicles development and maturation compared with House standard FSH.