Volume 31 of Epidemiologic Reviews, which accompanies this issue of the Journal, focuses on health disparities. Research on “differences”—that is, comparing groups of people who differ with respect to a health condition or risk factor—is the core of epidemiologic research. “Disparities” research is the field of epidemiology that seeks to understand and eliminate health differences derived from systematic, persistent discrimination against disadvantaged social groups (1). In this issue of Epidemiologic Reviews, James makes the case that “the current global attention on health disparities reduction is arguably best understood as the legacy of an implicit human rights-inspired paradigm shift in epidemiologic research that began in the middle of the 20th century”