Objective To evaluate whether delayed initiation of gonadotropin in luteal long protocol affected the outcome of in vitro fertilization (IVF).Study design Prospective randomized study at the reproductive centre of a university-based hospital.85 subfertile women undergoing IVF-ET (embryo transfer) after a standardized GnRHa long protocol.The patients were randomized into group A (stimulated 3 weeks after GnRHa administration)and group B (stimulated 2 weeks after GnRHa administration), according to the time of gonadotropin initiationafter GnRHa-mediated pituitary suppression.