Prediction of ovarian responses prior to stimulation is not only useful for patient counseling, but also important in tailoring the optimal dosage of gonadotrophin for individual patients. By prospectively study of 214 women undergoing in vitro fertilization and embryo transfer (IVF-ET) treatment, we obtained data supporting that antral follicle size could be an additional valuable predictive marker other than the antral follicle count (AFC) in predicting ovarian response. Our studies revealed that AFC achieved the best predictive value in relation to the number of oocyte obtained, followed by antral follicle size, basal follicle stimulating hormone (FSH) and body mass index (BMI). Unlike AFC, antral follicle size was noted to be negatively correlated with the dosage (R = -0.493) and duration (R = -0.465) of rFSH stimulation. Antral follicle size was also found with higher negative regression coefficient (B = -0.661) as compared with that of basal FSH concentration (B = -0.326) and BMI (b = -0.281). More importantly, women with antral follicle size 6-7mm showed significantly higher AFC, oocytes retrieved, fertilized oocytes and grade I/II embryos along with much lower transfer cycle cancellation rate (7.5% vs. 16-17%). Together, our data suggest that basal antral follicle size could be a valued predictive marker in women with IVF-ET treatment, in which women with antral follicle size 6-7mm are likely predisposed to better IVF-ET outcomes.