Krieger, NancyWilliams, David R.Objectives. This study determined the effects of changing from the 1940 to the 2000 standard million on monitoring socioeconomic and racial/ethnic inequalities in health. Methods. Using the 1940, 1970, and 2000 standard million, we calculated and compared ageadjusted rates for selected health outcomes stratified by socioeconomic level. Results. Changing from the 1940 to the 2000 standard million markedly reduced the age-adjusted relative risks for self-reported fair or poor health status of poor Americans compared with high-income Americans. Conclusions. Public health researchers and practitioners should give serious consideration to the implications of the change to the 2000 standard million for monitoring social inequalities in health.Health EquityHealthDisparitiesPublic HealthResearchracial/ethnicraceethnicitysocioeconomicinequalityArticle