Race, although an unscientific concept, remains prominent in health research and clinical guidelines, and is routinely invoked in clinical practice. In interviews with 58 primary care clinicians we explored how they understand and apply concepts of racial difference. We found wide agreement that race is important to consider in clinical care. They explained the effect of race on health, drawing on common assumptions about the biological, class, and cultural characteristics of racial minorities. They identified specific race-based clinical strategies for only a handful of conditions and were inconsistent in the details of what they said should be done for minority patients. We conclude that using race in clinical medicine promotes and maintains the illusion of inherent racial differences and may result in minority patients receiving care aimed at presumed racial group characteristics, rather than care selected as specifically appropriate for them as individuals.