Associations have been suggested between handedness, autoimmune disorders, and reproductive hormonal changes. The purpose of this study was to test a proposed relationship between handedness and age at menopause. Two national survey data sets were used to compare recalled ages at menopause. Mexican-American women, ages 35-74, naturally postmenopausal for at least 1 year, were selected from the Hispanic Health and Nutrition Examination Survey (HHANES). White and black women were selected from the National Health and Nutrition Examination Survey (NHANES-I) using similar criteria. The mean age at menopause was found to be earlier among left-handed women than right-handed women from the NHANES-I data set. In the HHANES data set, the mean age at menopause was significantly earlier among left-handed women than in right-handed women (t = 2.35, P less than .05). Early age at menopause among left-handed women may result from misclassification of handedness among older women or differential mortality among left-handed individuals. Alternatively, the association may be related to possible correlations between left-handedness and autoimmune disorders, which may include reactions against hormone receptor sites and oocytes.