Current electronic health record systems are primarily clinical in focus, designed to provide patient-level data and provider-level decision support. Adapting EHR systems to serve public health needs provides the possibility of enormous advances for public health practice and policy. In this review, we evaluate EHR functionality and map it to the three core functions of public health: assessment, policy development, and assurance. In doing so, we identify and discuss important design, implementation, and methodological issues with current systems. For example, in order to support public health's traditional focus on preventive health and socio-behavioral factors, EHR data models would need to be expanded to incorporate environmental, psychosocial, and other non-medical data elements, and workflow would have to be examined to determine the optimal way of collecting these data. We also argue that redesigning EHR systems to support public health offers benefits not only to the public health system but also to consumers, health-care institutions, and individual providers.