The effects of clomiphene citrate on endometrial nuclear estradiol receptors and progesterone receptors were examined in 10 normal women during an untreated cycle (control) and during treatment with 50 mg clomiphene citrate and 150 mg clomiphene citrate daily on days 5 through 9. Concentrations and binding constants of the receptors were determined in endometrium obtained 8 to 12 days after midcycle luteinizing hormone surge. Scatchard plots for both estrogen receptors and progesterone receptors were linear, indicating only one type of high-affinity binding sites. In control cycles, estrogen receptor levels (mean +/- SEM) were 199.6 +/- 23.1 fmol/mg deoxyribonucleic acid, (n = 8) and were not significantly different from either 50 mg clomiphene citrate (180.5 +/- 19.1 fmol/mg deoxyribonucleic acid, n = 6) or 150 mg clomiphene citrate (194.3 +/- 35.2 fmol/mg deoxyribonucleic acid, n = 4). Similarly, the dissociation constants were unaffected by clomiphene citrate treatment. The concentrations of progesterone receptors in the control cycles (613 +/- 31 fmol/mg deoxyribonucleic acid, n = 5) and treatment cycles (50 mg clomiphene citrate -652.8 +/- 121 fmol/mg deoxyribonucleic acid, n = 6; 150 mg clomiphene citrate -592.6 +/- 31 fmol/mg deoxyribonucleic acid, n = 7) were also not significantly different. Clomiphene citrate also did not affect dissociation constants for progesterone receptors. Therefore, ovulation induction with clomiphene citrate apparently did not affect peri-implantation phase endometrial estrogen receptors and progesterone receptors or their respective binding constants.