Differences in age at natural menopause by occupation, education, and place of residence were examined using a cross-sectional population sample of Finnish women aged 45-64 years (n = 1,713, response rate 86%). The sample was selected at random from the Finnish Population Register in 1989 (final n = 1,505, 75%). Kaplan-Meier estimates showed the median age at natural menopause to be 51 years for all women (95% confidence interval (CI) 50.6-51.4). The median menopausal age of smokers and nulliparous women was 50 years; that of nonsmokers and women whose first full-term pregnancy occurred before the age of 25 years was 52 years. Differences between occupational and educational groups were statistically significant (Mantel-Cox test for occupation, p < 0.02; for education, p < 0.03). In the Cox proportional hazards model, the odds ratio of the occurrence of natural menopause among upper white-collar women was 0.74 (95% CI 0.57-0.96) and among the most educated women (education > 11 years) it was 0.75 (95% CI 0.59-0.96), adjusted to reflect smoking, use of hormones, body mass index, and age at first full-term pregnancy. Sociodemographic variables appear to be associated with age at natural menopause in a representative sample of Finnish women.