Striking changes of ovarian function occur with aging. These changes begin subtly with reductions of fecundability being observed after age 25. The transition from reproductive to postreproductive life is characterized by menstrual irregularity including anovulation, or short luteal phases. The most prominent hormonal changes at the menopause are drastic reductions of estradiol and progesterone secretion by the ovary, reflecting the cessation of folliculogenesis and ovulation. Elevations of gonadotropins and reduction of inhibin levels also reflect the loss of folliculogenesis and ovulation. There are accompanying decreases of ovarian androgen secretion; however, the postmenopausal gonad directly secretes more testosterone after, than before, the menopause.