Epidemiological data indicate that women are less likely to suffer from coronary heart disease (CHD) than men of the same age. This difference vanishes however after menopause suggesting that it is the hormones produced by the ovaries that are responsible for the relative cardioprotection that women enjoy before menopause. In spite of the favorable impact of oral estrogen treatments on the lipid profile it is believed today that estrogens act mainly through direct effects on vessels. Estrogens have vasodilative properties, exert anti proliferative effects on the endothelium and alter the response of vessels to various stimuli (vaso-reactivity) such as Acetylcholine (Ach). Direct assessment of large vessel wall thickness or Intima Media Thickness (IMT) is considered as the most predictive parameter of cardiovascular risk today and may serve to single out women who must receive HRT for cardiovascular reasons.