UK policy promotes third sector organisations as providers of NHS funded health and social care. We examine the evidence for this policy through a systematic literature review. Our results highlight several problems of studies comparing non-profits with other provider forms, questioning their usefulness for drawing lessons outside the place of study. Most studies deem contextual factors and the regulatory framework in which providers operate as much more important than ownership form. We conclude that the literature does not support the policy of a larger role for the third sector in healthcare, let alone a switch to a market-based system.