Hysterectomy is the most frequently performed major operation. Its frequency is increasing due to greater use of elective indications such as uterine cancer prophylaxis, contraception, and menopausal problems. The effects of elective simple hysterectomy are evaluated in terms of morbidity and mortality rates and costs. Among 35-year-old women operated upon, the average over-all gain in life expectancy is only 0.2 years. This is due to the saving of 1.3 per cent of women who would have died from cancer of the cervix or endometrium; they gained 14.3 years of life. In addition, 3 per cent of women are spared the development of and treatment for these two conditions. All women operated upon would be relieved of some undesirable aspects of the menopausal years such as irregular uterine bleeding. There are also economic gains. However, the operation has adverse health effects which could offset any gains from cancer prevention. In addition, each year of life saved would cost about $12,800 and most of the added years would be lived in old age. Delaying the operation to age 45 and including oophorectomy would result in a lower cost per year of life saved-about $9,800-but the risk of adverse health effects probably would be increased very much. Cancer prophylaxis cannot justify elective hysterectomy; we cannot assess whether quality-of-life considerations do.