This response takes up four of Eric Arnesen's many objections to whiteness research: (1) the fuzziness of the definitions for “whiteness”; (2) the notion of a process by which European immigrants “became white”; (3) the sloppy research methods; and (4) the political posturing of some authors. Although I consider a range of works, I concentrate mainly on those of David Roediger. A serious analysis of the roots of white working-class racism was long overdue, and Roediger and his colleagues have advanced this study significantly. They have demonstrated the severe social limits and the racist implications of labor republicanism, an organizing principle for so much nineteenth-century labor history. They have placed racial identity at the center of class analysis and focused attention on the racialized character of class experience and consciousness. The notion of socially constructed understandings of race has also stimulated a more interethnic approach in studies of immigrant workers, and helped to bridge the obvious divisions between labor history and African-American, Asian-American, and Latina/o history. The study of whiteness has helped us to “denaturalize” race and look much more closely at the whole idea of white identity. We are due for a critical evaluation of this literature from the perspective of labor history, but it is far too early to discard the concept of “whiteness.” On the contrary, the most important work, in the form of rigorous studies of particular workplaces, unions, and communities, is really just beginning. In the meantime, the work has stimulated some much-needed rethinking.