Clinical index is needed to predict the outcome of pregnancy after in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) for infertile patients. Growth differentiation factor-8 (GDF-8), also known as myostatin, is one of transforming growth factor-â superfamily localized in antral follicles in normal and PCOS ovaries but its function in female reproductive system is still unknown. Aim of the study is to assess the correlation between levels of GDF8 in follicular fluid (FF) with outcomes of in vitro fertilization (IVF/ICSI) in women with and without PCOS. A prospective case control study was performed enrolling (40) patients with PCOS and (40) non-PCOS women (male infertility) undergoing IVF/ICSI. The collection of follicular fluid was at the day of oocyte pick up. Sandwich enzyme-linked immunosorbent assay (ELISA) kit was used to measure the levels of FF. GDF-8. A significant higher GDF8 level was found in PCOS group compared to non-PCOS group. Also, significant higher antral follicle count (AFC) in PCOS group in comparison tonon-PCOS group. There were no significant differences between the two groups in the mean of follicle diameter, endometrium thickness, aspirated oocytes, metaphase II (M II) oocyte, fertilized oocytes, embryo at 2pro nucleus (2PN), transferred embryo, grade1 (G1) embryo, maturity rate, cleavage rate, fertilization rate and pregnancy outcomes. There was a significant positive correlation between GDF8 and G1 embryo in non-PCOS group. In non-PCOS group, mean GDF8 level was significantly higher in pregnant group than nonpregnant group. In PCOS group, mean GDF8 level was significantly.