Over the last decade, compelling evidence supports the idea that the different impact of cardiovascular disease (CVD) and the differences in vascular biology in men and women may be, at least in part, related to the cardiovascular and metabolic effects of sex steroid hormones. Indeed, androgens and oestrogens influence a multitude of vascular biological processes and their cardiovascular effects are multifaceted. While in women the effects of androgens mainly depend upon oestrogens' levels and, ultimately, upon the estradiol/testosterone ratio, the effects of androgens in men mostly relate to their aromatization into oestrogens. Oestrogens exert potential beneficial effects on the cardiovascular system in both sexes. In women, the effect of oestrogens, alone or in association with progestins, has been widely investigated, but data obtained from older patient populations have lead the medical community and the general public to misleading conclusions. Growing evidence supports the 'timing hypothesis', which suggests that oestrogen/hormone replacement therapy may increase CVD risk if started late after menopause, but produce beneficial cardiovascular effects in younger postmenopausal women. Because in men adequate interventional studies with testosterone are lacking, specific investigations should be performed.