To review and summarize current evidence on the health consequences of premature menopause and early menopause.We reviewed existing literature and combined graphically some results from the Mayo Clinic Cohort Study of Oophorectomy and Aging.Premature menopause or early menopause may be either spontaneous or induced. Women who experience premature menopause (before age 40 years) or early menopause (between ages 40 and 45 years) experience an increased risk of overall mortality, cardiovascular diseases, neurological diseases, psychiatric diseases, osteoporosis, and other sequelae. The risk of adverse outcomes increases with earlier age at the time of menopause. Some of the adverse outcomes may be prevented by estrogen treatment initiated after the onset of menopause. However, estrogen alone does not prevent all long-term consequences, and other hormonal mechanisms are likely involved.Regardless of the cause, women who experience hormonal menopause and estrogen deficiency before reaching the median age of natural menopause are at increased risk for morbidity and mortality. Estrogen treatment should be considered for these women, but may not eliminate all of the adverse outcomes.