Ten women with infertility, regular menses, and elevated plasma FSH concentrations after a failed in vitro fertilization attempt were studied throughout a spontaneous menstrual cycle. Plasma estradiol, progesterone, inhibin, LH, and FSH concentrations were measured by RIA on days 1, 8, 15, and 22 and compared with the ovarian steroid and gonadotropin profiles obtained from seven endocrine-normal women. The elevated FSH concentrations in the hypergonadotropic group were not associated with significant changes in E2 and P4, but an increase in LH concentrations was found on days 1, 8, and 22 (medians of 18 and 4, 17 and 6, and 7 and less than 3 U/L for the hypergonadotropic and normal groups, respectively; P less than 0.01). Their plasma inhibin concentrations [213, 242, 747, and 561 U/L (median values on days 1-7, 8-14, 15-21, and 22-28)] were normal. Autoantibodies to adrenal, thyroid, or ovary were present in five (50%) women, and antiovarian antibodies were present in 4. Two women gave a family history of thyroid disease, and one woman was hypothyroid. Repeat assessment 3-6 months revealed persistently elevated FSH concentrations in five (63%) of eight women; the other three had normal ovarian steroid and gonadotropin concentrations. The triad of infertility, regular menses, and elevated plasma FSH concentrations describes a group of women with occult ovarian failure, a condition of compensated granulosa cell function, which may be an early stage of premature ovarian failure. These women with occult ovarian failure had an impaired response to ovarian hyperstimulation and may be at increased risk of developing polyglandular autoimmunity.