There are well-known Black-White disparities in adverse birth outcomes, health behaviors, and chronic diseases such as asthma, diabetes, and hypertension. These disparities hold across socioeconomic status and have remained stable for the past 50 years despite efforts to reduce them. This theoretical review argues that such disparities may be largely a function of residential segregation, ie, the separate and unequal neighborhoods in which most Blacks and Whites reside irrespective of their socioeconomic status. We review evidence that Black neighborhoods have significantly poorer healthcare facilities staffed by less competent physicians, higher environmental exposures, and poorer built environments than do White neighborhoods, and we argue that these neighborhood disparities are 3 pathways through which segregation contributes to health disparities. We summarize the research needed on the role of segregation in health disparities and emphasize the hypothesis that these may be differences between Whites and segregated Blacks alone.