In 1977, the federal Office of Management and Budget (OMB) established an official classification standard for the measurement of race in the American population. In so doing, the OMB authorities created what amounted to a racial cosmology that spread throughout American society, affecting public perceptions about the racial hierarchy of American society. In 1997, the OMB issued a revised version of this classification in which small changes may profoundly affect the way policymakers and the American public think about race. At the very least, these revisions present significant challenges to social scientists who study race and ethnicity. This review begins with a brief historical overview of racial data collected by the federal government. It subsequently examines the circumstances leading up to the 1997 revisions of OMB Directive No. 15 and discusses how these revisions may affect social scientific research on the subject of race and ethnicity.