Forty women with normal menstrual cycles who had been sterilized by tubal ligation or electrocoagulation requested tubal reconstruction. As part of their preoperative evaluation, progesterone measurements were obtained in the midluteal phase (5–10 days before the next menstrual period). This group of women had a significantly lower (P < 0.005) mean midluteal progesterone level (9.4 ± 4.7 ng/ml) than a control group of 24 women with infertile male partners attending the same clinic (17.4 ± 7.1 ng/ml). In 25 (62%) of the sterilized women, progesterone levels were ≤ 10 ng/ml, whereas in the control group such low values were found in only 4 (17%) of the women. Thus, reduced midluteal serum progesterone concentration appears more common among women with prior tubal ligation or electrocoagulation than among a control population of apparently normal women.