PURPOSE: The patient-centered medical home is evolving as an approach to providing primary care. Primary care is defined by four main characteristics: comprehensive, coordinated, continuous, and accessible care, all of which are measurable. This analysis identifies tools for determining whether a patient-centered medical home achieves high level primary care. DESIGN: Instruments for measuring primary care were reviewed. METHOD: Tools were reviewed for population coverage, format, testing of validity and reliability, and inclusion of the attributes of primary care. PRINCIPAL FINDINGS: Only one tool, the Primary Care Assessment Tool (PCAT), scored highly on primary care features, as it was designed to assess both structural and process features of primary care and is available in multiple user formats. CONCLUSION: Based on the evidence supporting the relationship between primary care, improved population health, and reduced health care costs, measurement of primary care transformation approaches such as the medical home can and should include specific measurement of the services associated with the four core attributes of primary care.