OBJECTIVE To compare the effects of oral contraceptive (OC) pill pretreatment in recombinant FSH/GnRH-antagonist versus recombinant FSH/GnRH-agonist stimulation in in vitro fertilization (IVF) patients, and to evaluate optimization of retrieval day. METHODS Prospective, randomized, multicenter study. METHODS Private practice and university centers. METHODS Eighty patients undergoing IVF who met the appropriate inclusion criteria. METHODS Four study centers recruited 80 patients. The OC regimen began on cycle days 2 to 4 and was discontinued on a Sunday after 14 to 28 days. The recombinant FSH regimen was begun on the following Friday. The GnRH-agonist group was treated with a long protocol; the GnRH-antagonist was initiated when the lead follicle reached 12 to 14 mm. When two follicles had reached 16 to 18 mm, hCG was administered. METHODS The primary outcome measures were the number of cumulus-oocyte complexes, day of the week for oocyte retrieval, and total dose and days of stimulation of recombinant FSH. Secondary efficacy variables included pregnancy and implantation rate; serum E(2) levels on stimulation day 1; serum E(2), P, and LH levels on the day of hCG administration; follicle size on day 6 and day of hCG administration; the total days of GnRH-analogue treatment; total days on OC; total days from end of OC to oocyte retrieval; and the cycle cancellation rate. RESULTS Patient outcomes were similar for the days of stimulation, total dose of gonadotropin used, two-pronuclei embryos, pregnancy (44.4% GnRH-antagonist vs. 45.0% GnRH-agonist, P=.86) and implantation rates (22.2% GnRH-antagonist vs. 26.4% GnRH-agonist, P=.71). Oral contraceptive cycle scheduling resulted in 78% and 90% of retrievals performed Monday through Friday for GnRH-antagonist and GnRH-agonist. A one day delay in OC discontinuation and recombinant FSH start would result in over 90% of oocyte retrievals occurring Monday through Friday in both groups. CONCLUSIONS The OC pretreatment in recombinant FSH/GnRH-antagonist protocols provides a patient-friendly regimen and can be optimized for weekday retrievals. No difference was seen in number of 2PN embryos, cryopreserved embryos, embryos transferred, implantation and pregnancy rates between the two stimulation protocols.