Hyaluronic acid (HA) is an anionic, non-sulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. The study included 40 infertile females. A full history taking, complete general examination, complete gynecological examination, and infertility workup including basal hormonal analysis, and uterine cavity assessment by ultrasound and tubal patency evaluation by hysterosalpingogram was done in addition to husband’s seminal fluid analysis. The control group did not receive any ovarian stimulation drugs, while the 2nd group was treated with letrozole + gonadotropin. The ovarian stimulation protocol was chosen for each patient according to her age, history, and hormonal assay. Evaluation of thickness and pattern of the endometrium, size, and the number of mature follicles was performed by transvaginal ultrasonography on the 2nd day of the menstrual cycle and cycle day 11-14 before hCG injection. The study showed no correlation between HA and LH at triggering day in women who received letrozole plus Gonadotropin but a positive correlation was documented between HA concentration and E2 in addition to a positive correlation with progesterone, the number of follicles, and endometrial thickness at the day of triggering of ovulation. The study revealed that mean hyaluronic acid concentration was elevated significantly (P<0.05) in pregnant women after stimulation protocol compared with nonpregnant (164.2 vs. 152.1 pg/ml). HA was significantly higher in women who undergo ovarian stimulation with letrozole which was a good protocol in the treatment of women with ovulatory problems.