Primary care access for Medicaid patients is an ongoing area of concern. Most studies of providers' participation in Medicaid have focused on factors associated with the Medicaid program, such as reimbursement rates. Few studies have examined the characteristics of primary care practices associated with Medicaid participation. We used a nationally representative survey of primary care practices to compare practices with no, low, and high Medicaid revenue. Seventeen percent of practices received no Medicaid revenue; 38 percent and 45 percent were categorized as receiving low and high Medicaid revenue, respectively. Practices with no Medicaid revenue were more often small, independent, and located in urban areas with higher household income. These practices also have lower population health capabilities.