Purpose: To establish the serum pattern for glycodelin and to investigate the possible correlations of serum and follicular fluid (FF) glycodelin with clinical pregnancy in gonadotropin-releasing hormone (GnRH)-antagonist controlled cycles. Materials and Methods: A prospective observational study conducted with 80 infertile couples who received a GnRH-antagonist controlled cycle. Glycodelin levels were measured in FF, day 2-3, and ovarian pick-up (OPU)-day serum samples. Results: There were no significant differences in serum glycodelin concentrations in either the early follicular phase or the preovulatory phase, and in FF glycodelin concentrations between clinically pregnant and non-pregnant patients. OPU-day serum glycodelin was found to be significantly higher than early follicular serum glycodelin level in all patients whether pregnancy occurred or not Conclusion: Although day 2-3 and OPU-day measurements of serum glycodelin levels were not significant in predicting clinical pregnancy, the pattern of serum glycodelin seems different in GnRH-antagonist controlled cycles than natural and GnRH-agonist controlled cycles.