To inform WHO’s Strategy Report on engaging the private health service delivery sector through governance in mixed health systems, Barbara O’Hanlon & Dr. Mark Hellowell analyzed current global health practice in the domain of engagement of the private sector (Private Sector Landscape in Mixed Health Systems, Study 5). This analysis included mapping of the history of engagement of the private sector in health, beginning with large vertical health programs and moving towards market-based approaches. The findings are presented in three “stages”.