Racial and ethnic disparities in primary health care likely reflect the aggregate socioeconomic composition of a physician's patient panels as well as differences in individual patients' characteristics. National physician survey data indicate that physicians in high-minority practices depend more on low-paying Medicaid, receive lower private insurance reimbursements, and have lower incomes. These constrained resources help explain the greater quality-related difficulties delivering care reported by these physicians--such as coordination of care, ability to spend adequate time with patients during office visits, and obtaining specialty care--that relate directly to physicians' ability to function as their patients' medical home.