Interactions of the private and public sector within national health systems are manifold and not always well understood, and the decision to purchase services is often made in poorly regulated health systems with limited public capacity for health governance. This may lead to unintended consequences from purchasing services from one group of providers. This Policy Brief focuses on the rationale and potential arrangements by which governments could purchase primary health care services from the private sector for currently underserved populations. It aims to provide a structured guide to assist decision-making and selection of purchasing options.