BackgroundThe presence of health inequalities is one of the largest issues currently facing public health policy making in developed countries. Interventions that engage the community in their design or delivery are thought more likely to address the specific needs of disadvantaged populations, and community engagement has consequently become central to guidance and strategies for promoting public health. We aimed to map the evidence on community engagement approaches to address health inequalities, with a focus on the mechanisms of engagement used, and to consider the coverage of current evidence to inform policy making on health inequalities. MethodsWe did systematic searches for systematic reviews to identify relevant controlled trials assessing public health interventions with members of the community searching these databases using web interfaces: DoPHER, Campbell, Cochrane Reviews library, DARE, HTA database, and Web of Knowledge HTA search. Systematic reviews were used as a source because of the systematic way in which they describe included studies. The search was limited to studies that address health inequalities, either through targeting a disadvantaged population or through subgroup analyses, and that were done in developed (OECD) countries. We extracted data from the studies (using independent quality assurance procedures) and judged their quality using the Cochrane Risk of Bias method. Data were obtained on the mechanisms through which the community were involved, the health issue targeted by the intervention, and characteristics of the sample or population and intervention. Data were held in EPPI-Reviewer 4 and all reports of relevant studies were included, making no distinction between published or unpublished sources. We mapped the aims of the interventions in our review with the six policy objectives proposed in the UK Marmot review (2010) to establish the extent to which there was evidence to inform policy in this area. For example, we looked at how many studies addressed the objective of getting the best start in life through a focus on issues such as breastfeeding and antenatal care. FindingsWe identified 361 reports of 319 studies meeting our criteria. Most contained some form of health education about topics, including sexual health (60) or healthy eating (31). Almost half the studies included the community in the design or planning of the intervention through consultation or collaboration. Almost three-quarters were led by, or delivered in collaboration with, community members; only a quarter encompassed the community in the assessment of the intervention. In terms of overlap with UK health inequalities policy objectives, 219 studies addressed a social determinant of health or modifiable risk factor prioritised in the Marmot review (eg, 64 studies assessed ill health prevention); some modifiable risk factors were in fewer studies (eg, 14 studies assessed sustainable and safe places and communities). InterpretationDespite some gaps, public health science provides a wealth of evidence about community engagement to address health inequalities, which could be used to inform policy making. Outputs from this project include a new conceptual framework and analysis of the effectiveness and cost-effectiveness of such approaches. FundingThis Abstract refers to independent research commissioned by the National Institute for Health Research.