Thirty years after the civil rights era, the United States remains a residentially segregated society in which Blacks and Whites inhabit different neighborhoods of vastly different quality. Given high levels of racial segregation and elevated rates of Black poverty, it is axiomatically true that African Americans will experience more neighborhood poverty than other groups. Moreover, because poverty is associated with crime and delinquency, they will also be exposed to far higher rates of social disorder and violence. In this article I argue that long-term exposure to social disorder and violence because of segregation produces a high allostatic load among African Americans, which leads, in turn, to a variety of deleterious health and cognitive outcomes. After summarizing recent research on stress and allostatic load, I specify a biosocial model of racial stratification and draw upon it to explicate well-documented racial differentials with respect to health and cognition.