Twenty-two infertile women with repeated deficient results in the postcoital test received clomiphene citrate or tamoxifen. The patterns of luteinizing hormone, follicle-stimulating hormone, prolactin, 17 beta-estradiol (E2), and progesterone were examined during the follicular and periovulatory phases of the menstrual cycle, as were the cervical mucus characteristics. Under clomiphene treatment, an overproduction of E2 was observed (P less than 0.01), which did not result in an improvement of the cervical mucus characteristics. The pH of the endocervical mucus was lower (P less than 0.01). Under tamoxifen treatment, the serum E2 levels were higher (P less than 0.05) and normalized. Higher spermatozoa penetration meter scores were observed during the preovulatory and periovulatory periods, whereas the pH of the endocervical mucus was not lowered. These data support that tamoxifen may be preferential to clomiphene in treating this kind of infertile woman.