The effects of different monophasic combinations of ethinyl estradiol and norethindrone on FSH, LH, sex hormone binding globulin, total testosterone, androstenedione, and dehydroepiandrosterone sulfate levels in non-obese, non-hirsute women were compared. Retrospective analysis of frozen serum from a prospective randomized trial in which women received one of three oral contraceptive pills containing ethinyl estradiol 50 micrograms/norethindrone 1 mg, ethinyl estradiol 35 micrograms/norethindrone 1 mg or ethinyl estradiol 35 g/norethindrone 0.5 mg for nine cycles was conducted. Blood samples were obtained prior to treatment and during the third, sixth and ninth pill cycles. Ethinyl estradiol 50 micrograms/norethindrone 1 mg and ethinyl estradiol 35 micrograms/norethindrone 1 mg suppressed FSH, LH, and total testosterone and increased sex hormone binding globulin to a similar degree. Ethinyl estradiol 35 micrograms/norethindrone 0.5 mg resulted in less suppression of FSH, LH, and total testosterone, but greater elevation of sex hormone binding globulin. Dehydroepiandrosterone sulfate was suppressed to a similar degree with ethinyl estradiol 35 micrograms/norethindrone 1 mg and ethinyl estradiol 35 micrograms/norethindrone 0.5 mg, but ethinyl estradiol 50 micrograms/norethindrone 1 mg resulted in the least suppression of dehydroepiandrosterone sulfate. Ethinyl estradiol 35 micrograms/norethindrone 1 mg caused greater suppression of androstenedione than did the other two oral contraceptives. Oral contraceptive-induced changes in gonadotropins, androgens, and sex hormone binding globulin can be predicted by considering the relative amounts of estrogen and progestin in the pill. When combined with 1 mg of norethindrone, 50 micrograms of ethinyl estradiol did not result in greater suppression of FSH, LH, or total testosterone or in greater elevation of sex hormone binding globulin than did 35 micrograms of ethinyl estradiol.