to examine the possible effects of aging on circulating steroid hormones in postmenopausal women, blood samples were drawn from 155 women, aged 34 to 83 years, with spontaneous ovarian failure. The C-21 steroids, pregnenolone and 17-hydroxypregnenolone; the delta 4 progestins, progesterone and 17-hydroxyprogesterone; and cortisol did not change with age and were similar in concentration to the levels measured during the follicular phase of premenopausal women. The delta 5 androgens, dehydropiandrosterone and dehydroepiandrosterone sulfate, declined significantly (P less than .001) with age, whereas no change was noted in the delta 4 androgens, androstenedione and testosterone. The levels of estradiol (E2) and estrone (E1) were strongly correlated with percent ideal weight but did not change with age. The authors conclude that 1) The production of progestins does not change with age in normal adult women, other than that resulting from the loss of secretion associated with ovarian corpus luteum function. 2) The decline of delta 5 androgens without corresponding changes in their precursors suggests an age-related change of adrenal 17,20 desmolase activity. 3) The levels of E2 and E1 reflect an effect of body size but not of age on peripheral aromatization of precursor androgens.