In in vitro fertilization (IVF) cycles using gonadotropin-releasing hormone agonist (GnRH-a) suppression, we investigated whether an elevated progesterone (P) level on the day of human chorionic gonadotropin (hCG) administration indicates premature luteinization and is associated with a lower pregnancy rate. We retrospectively studied 101 patients treated with the GnRH-a leuprolide acetate, begun in the luteal phase of the prior menstrual cycle and continued until the day of hCG administration. On the day of hCG, 72 patients had P less than 0.9 ng/mL and 29 had less than or equal to 0.9 ng/mL. Patients in the high P group had a significantly greater estradiol level on the day of hCG. No significant difference in clinical pregnancy rates or ongoing pregnancy rates occurred between the low P and high P groups. We conclude that in IVF cycles pretreated with GnRH-a, P levels on the day of hCG are not predictive of conceiving in that cycle.