Although hormone replacement therapy (HRT) has been available for almost 100 years, conflicting opinions still exist about its efficacy and safety. There is uniform agreement that vasomotor instability and vaginal atrophy are totally reversible with HRT. Effective treatment of bone loss with HRT depends on the number of years of estrogen deprivation, peak bone mass, and rapidity of bone loss. Oral, transdermal, and pellet estrogens are equality effective. Mortality from coronary heart disease decreased 20% to 40% in women on HRT, yet the mechanism has not yet been ascertained. The increased risk of endometrial cancer has been confirmed, but better diagnostic techniques for detection in the precancerous state have been developed. The relationship of breast cancer to estrogen use has not been conclusive. Meta-analysis of 13 studies results in a relative risk of 1.06, whereas a large case-control study reveals a relative risk of 0.9. However, it is clear that in the average, healthy woman, low-dose estrogen replacement for less than 10 years does not increase the risk of breast cancer. Physicians are encouraged to help patients weigh the risks and benefits of HRT.