This review describes the clinical usefulness of transdermal hormone replacement therapy. This route of administration is particularly important in women with hypertriglyceridemia, in hypertensive postmenopausal women, in women who smoke or have an increased risk of biliary or liver disorder, for those who display a reduced glucose tolerance or in women who are at risk of thrombotic disorders. The avoidance of the "first passage effect" is ensured by the transdermal application of estrogen and probably explains the superiority of this route of steroid administration.