Abstract: The UK Government's recent policies to tackle the causes of health and social inequalities, as well as modernising health services presents a new challenge for the Cochrane Collaboration. Each health district is required by law to develop 3 year health improvement plans in partnership with other sectors including social care, education and the voluntary sector. In areas of high deprivation, special 'Health Action Zones' have been established, providing extra resources for new initiatives to improve health and re-configure all services, in partnership with the communities themselves. These new policies, which recognise the wider determinants of health outside health services are a welcomed change. However, many questions remain unanswered: Will it work? What role does systematic evidence play in health improvement and tackling inequalities? How can evidence for health improvement be used where much emphasis is placed on community ownership and participation? The presentation will describe the background of one Health Action Zone and how systematic evidence is playing an important role in addressing these questions. Over 120 health improvement initiatives have been grouped into subject areas. Effectiveness questions raised by these projects have been appraised against current evidence of effectiveness (using public health evidence summaries developed by the UK Cochrane Centre). We found that further assessments of projects aiming to improve health and the relevance of systematic evidence to those projects could only be assessed with those running projects. The presentation will therefore describe the outcome of evidence-based workshops for project and community leaders, and explore the ethical dilemmas this raised between genuine community ownership versus the technical/evidence-based approach to health improvement decision