Ethnic-racial diversity in the United States is a source of national pride, but it is overshadowed by the reality that stigmatized groups are disproportionately burdened by negative physical health. The social contexts and their activated psychological processes that contribute to ethnic-racial health disparities are not well understood. Moreover, scientists should delineate the implications of their research for public policies that address health disparities. This <i>Journal of Social Issues</i> volume brings together social, developmental, cognitive, and clinical psychological research on health disparities. Furthermore, it discusses how the present research informs public health policy.