Hormone replacement therapy. How to select the best preparation and regimen. Hormone replacement therapy is a mainstay of preventive healthcare for the maturing female population. Estrogen deficiency that comes with menopause can have serious effects and is especially important in light of the increasing life expectancy of women. Various estrogen and progesterone preparations are available, and their best application requires understanding of the different potencies and metabolic effects. Daily maintenance therapy without a drug-free interval is becoming the standard method of the 1990s. No doubt the future will bring even better delivery regimens. 