Estrogen therapy has been well established as an effective treatment for relief of vasomotor symptoms. In light of recent evidence from large randomized trials showing serious risks associated with use of estrogen treatment, current recommendations for hormone therapy emphasize using the lowest effective dose for the shortest possible time. The purpose of this review is to examine what has been learned from the Women's Health Initiative (WHI) Hormone Trials and other studies about the short-term risks and benefits of estrogen use. A second purpose is to examine whether short-term risks differ for women most likely to use hormone treatment, including individuals with vasomotor symptoms; women in their 50s; and women, with and without intact ovaries, who have had a hysterectomy. During the first 1 to 2 years of use of conjugated equine estrogens alone (E-alone) or combined with medroxyprogesterone acetate (E + P), women experience an elevated risk of coronary heart disease, stroke, and deep vein thrombosis or pulmonary embolism. The magnitude of risk is greater for E + P than for E-alone. Fracture risk is not reduced with 1 to 2 years of use, but a fracture benefit is seen within 5 years of use. Increased risk of breast cancer does not appear until after 4 to 5 years of E + P use and was not increased with E-alone use after < or =7 years of treatment. This pattern of risks and benefits is generally similar for women with vasomotor symptoms, women in their 50s, and women, with and without > or =1 intact ovary, who have had a hysterectomy.