Review three is a realist synthesis of community engagement approaches to enhance trust and increase Gypsy/Travellers’ participation in health services. Four hypotheses, derived from published literature, were developed to provide initial direction for the review:Community engagement is an effective and cost-effective strategy for enhancing the confidence and trust of Gypsy/Travellers in mainstream services ;Approaches to community engagement that work to enhance trust and increase uptake of services with some participants may not work with Gypsy/Travellers because of the longstanding experience of social exclusion and discrimination, low education and literacy levels and mistrust of authority ;Successful community engagement will be underpinned by genuine involvement of community members (i.e. not tokenistic), honest appraisal of what can be achieved (not raising expectations that cannot be met) and continuity of trusted personnel .Community engagement between Gypsy/Travellers and mainstream health services can be facilitated effectively by civil society Gypsy/Traveller organisations [8, 39].