Data from the National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Followup Study were used to examine age differences in neuroticism, extraversion, and openness to experience. Cross-sectional analyses of data from 10,063 respondents showed that older subjects were slightly lower in neuroticism, extraversion, and openness; that age trends were not curvilinear; and that there were no differences in personality scores that might be attributable to a mild-life crisis or transition. Comparison with data from 654 participants in the Augmented Baltimore Longitudinal Study of Aging (ABLSA) showed that the ABLSA sample was lower in extraversion and higher in openness than the national sample, although the differences were small in magnitude. Results were interpreted to mean that sampling and attrition in this longitudinal sample did not seriously bias results on these personality variables, and that cross-sectional findings from a large probability sample support the conclusion that personality is predominantly stable in adulthood.