To determine the effects of female hormones on peripheral vasculature we studied the brachial artery circulation. Nine young women (27-37 yrs) having inactive ovaries received transdermal estradiol (E2) (0.1-0.4 mg/d) and vaginal progesterone (P) (300 mg/d) to duplicate the menstrual cycle levels of E2 and P. Brachial artery diameter, blood velocity and flow were measured by bidimensional pulsed Doppler in basal conditions, and during hand exclusion by a cuff inflated at suprasystolic pressure. Vascular resistance was calculated by the ratio of mean blood pressure over mean flow. Measurements were obtained before hormonotherapy (d0), on day 14 (d14, after E2), and on day 28 (d28, after E2 and P). The increase of brachial artery diameter began at d14 (3.73 +/- 0.12 mm, vs 3.66 +/- 0.11 mm; NS) to become significant at d28 (3.91 +/- 0.10 mm, p < 0.05). Blood velocity and flow increased at d28 (4.78 +/- 0.55 cm/s, vs 3.55 +/- 0.65 cm/s; P < 0.05 and 35.2 +/- 5.2 ml/mn vs 22.2 +/- 3.6 ml/mn, P < 0.05 respectively). No change was noted in mean blood pressure. The decrease of resistance began at d14, in order to be significant at d28 (158 +/- 17 mmHg/ml/s at d0 vs 263 +/- 31 mmHg/ml/s at d28; P < 0.05). Brachial vasoconstriction during hand exclusion, in response to low flow state disappeared at d14 with estradiol. In conclusion, in women deprived of ovarian function, physiological E2 and P replacement vasodilates small and large arteries, whereas E2 alone attenuates the large artery vasoconstriction in acute response to low flow state.(ABSTRACT TRUNCATED AT 250 WORDS)