Objective: To determine reference values for the midluteal plasma progesterone concentration. Design: Retrospective analysis. Setting: Infertility clinic at an academic medical center. Patient(s): One hundred ninety-two infertile women who became pregnant after induction of ovulation with hMG. Intervention(s): The plasma progesterone level was measured during the midluteal phase of the hMG treatment cycle. Main Outcome Measure(s): The midluteal plasma progesterone concentration was correlated with the outcome of the pregnancy. Result(s): In this cohort of 192 women in whom ovulation was induced with hMG and 5,000 IU of hCG, the mean midluteal plasma progesterone concentrations were 29.07 ng/mL, 25.85 ng/mL, 31.49 ng/mL, 41.39 ng/mL, and 28.64 ng/mL in all cycles that resulted in pregnancy, cycles that resulted in full-term singleton pregnancy, cycles that resulted in full-term multiple pregnancy, cycles that resulted in preterm pregnancy, and cycles that ended in miscarriage, respectively. There was no statistically significant difference in the progesterone concentration between the cycles that resulted in full-term pregnancy and those that ended in miscarriage, but there was a statistically significant difference between the cycles that resulted in singleton pregnancy and those that resulted in multiple pregnancy. The minimum value that was compatible with a full-term pregnancy in this cohort of women was 10.83 ng/mL. Conclusion(s): In a cohort of 192 women, the minimum plasma progesterone concentration on day 7 in women who attained a full-term pregnancy after induction of ovulation with 5,000 IU of hCG was 10.83 ng/mL.