Two patients were admitted to our Gamete Intrafallopian Transfer (GIF) program, and received and ovulation stimulation protocol with Clomiphene Citrate and human menopausal gonadotropin (hMG). Human chorionic gonadotropin (hCG, 10,000 IU IM) was administered when follicle size achieved 18 mm adn oocyte retrieval was scheduled after 36 hours. The estradiol levels in both patients were 1,127 pg/ml respectively at the time hCG was administered, which demonstrates an excellent response to the stimulation. Follicle aspiration was accomplished by transvaginal ultrasound-guided puncture or laparoscopy, and we were unable to recover oocytes in 17 follicles. Our findings support the existence of the "Empty Follicle Syndrome". This pathology may explain some of the infertility causes of our sterile population.