This project examines whether segregation by patient race and other demographics occurs in the context of primary care; and then considers the implications of segregation for disparities in health care use and outcomes. It documents the allocation of Medicare beneficiaries and other patients by race across primary care providers and, if we find racial segregation exists, we will explore contributory factors. We will determine the extent to which the delivery of physician services is racially segregated, and whether the degree of segregation has changed over time. We will identify the extent to which racial segregation varies across geographic areas and explore the drivers of those geographic differences. We will then evaluate whether racial segregation in the delivery of primary care is driven by the geographic location of physician practices and patient residences; or whether patient selection across providers, conditional on geographic location, contributes to racial segregation.