Hormone replacement therapy may reduce the risk of coronary heart disease but underlying mechanism has not been adequately explained. Recent data suggest that intercellular adhesion molecule 1 (ICAM-1) plays a critical role in early stage of atherosclerosis and may serve as a molecular marker for the development of arterial disease. We investigated the effects of oral and transdermal cyclic oestradiol combined with progesterone on plasma concentration of soluble ICAM-1 (sICAM-1). Thirty-seven healthy postmenopausal women were randomly assigned to receive either oral estradiol valerate or transdermal estradiol both combined with micronized progesterone or no hormonal treatment. Plasma sICAM-1 was assayed at baseline and after a 6-month period. Oral but not transdermal estradiol regimen significantly decreased mean value of sICAM-1 compared with no treatment. Differences in sICAM-1 levels between active treatments were significant. There were no significant changes in mean values of fibrinogen between the three groups. Our results show a favorable effect of oral estrogen plus progesterone on a soluble marker of vascular inflammation and may provide plausible explanation for a cardioprotective effect of hormone replacement therapy among healthy postmenopausal women.