Recent studies have demonstrated the presence of ovarian follicular development in up to 78% of women with premature ovarian failure (POF). The purpose of this study was to examine the control of FSH by estradiol and inhibin secretion from these follicles. Weekly blood samples were collected in conjunction with assessment of ovarian follicle development by ultrasound for at least 12 wk in 49 subjects with POF. Results were compared with those of 44 normal cycling women. Ovulatory cycles occurred in 24 subjects (49%) with POF. These ovulatory cycles were characterized by higher FSH and lower inhibin B and inhibin A levels, whereas estradiol levels were higher compared with those in normal women. Follicles developed in the absence of ovulation in 18 women (37%) with POF, whereas the ovaries were inactive in seven women (14%). FSH levels were lower in POF women with ovulatory or anovulatory follicle development compared with levels in women with inactive ovaries. These findings demonstrate that ovulatory cycles in women with POF are characterized by a persistent elevation in FSH compared with levels in normal cycling women. The association of increased FSH with lower levels of inhibin B and inhibin A, but higher estradiol levels provides additional evidence for an important physiological role of the inhibins in the negative feedback control of FSH. These data also demonstrate the variability in FSH levels as a function of underlying follicular development in women with POF.