Several medications have been found to increase implantation rates with in vitro fertilization (IVF) when given as adjuncts to follicle stimulating hormone (FSH) stimulation of the ovaries in preparation for oocyte retrieval. Gonadotropin-releasing hormone (GnRH) agonists, oral contraceptives (OCs), and estrogen pretreatment help to synchronize the follicular cohort resulting in an improved ovarian response. Metformin (MET) increases implantation in PCOS women having IVF and dramatically reduces the incidence of ovarian hyperstimulation syndrome (OHSS) in these women. Growth hormone (GH) markedly increases implantation in poor-responding women having IVF. Small doses of human chorionic gonadotropin (hCG) are used to provide LH activity allowing use of pure FSH products and the pen devices that deliver graduated FSH doses. Low-dose aspirin (ASA) increases ovarian response and implantation, and reduces the incidence of severe OHSS. Drugs such as letrozole that increase androgens may prove to be useful agents to increase ovarian response in poor responders.