In a cohort of 19,731 Norwegian postmenopausal women, the authors analyzed relations between the age at natural menopause and all-cause mortality. A total of 18,533 women died during the 37 years of follow-up from 1961 to 1997. An inverse relation was found between the age at menopause and the all-cause mortality rate (p = 0.003). The strength of the association was moderate, however, with 1.6% (95% confidence interval: 0.6, 2.7) reduced mortality per 3 years' increase in age at menopause. The impact appeared to be stronger in women with an attained age of less than 70 years (3.7% reduction in risk) than in women aged 80 years or more (1.0%). The inverse relation could not be explained by extreme mortality rates in women with very early (<40 years) or late (>55 years) menopause or by possible confounding variables like birth cohort, place of residence, occupational category (own or husband's occupation), body mass index, age at menarche, and first and last delivery or parity. The smoking prevalence was low in the underlying population, and the use of hormone replacement therapy was very rare. The authors conclude that age at natural menopause is inversely related to all-cause mortality.