Out-of-hours (OOH) services provide urgent primary care when primary care physician (PCP) offices are closed, most often from 5pm on weekdays and all day on weekends and holidays. Based on a policy survey (covering 27 OECD countries) and the existing literature, the working paper describes the current challenges associated with the organisation of OOH primary care and reviews the existing models of delivering OOH primary care. The paper pays particular attention to policies which have been pursued to improve access and quality of OOH primary care. Findings of the paper show that most OECD health systems report key challenges to provide OOH primary care in an accessible and safe way. These challenges relate to (i) PCPs’ reluctance to practise due to high workload and insufficient remuneration; and (ii) geographical variations in access to OOH primary care within each health system. Together these challenges are leading sources of inappropriate hospital emergency department (ED) visits. Results also indicate that several models of OOH primary care exist alongside each other in the 27 OECD countries participating in the policy survey. Hospital EDs, rota groups and practice-based services remain the most common OOH arrangements, but there is a tendency to shift OOH primary care towards primary care centres and large-scale organisations known as general practice cooperatives (GPCs). A range of solutions have been implemented to improve access and quality of OOH primary care across OECD countries. These include providing organisational and financial support to PCPs; using other health care professionals (such as nurse practitioners), making OOH care participation compulsory, setting up a telephone triage system, using new technologies, and developing rich information systems.