Child and adolescent mental health (CAMH) services in the UK have a long history of multiagency working. In this article, we explore the difficulties in agreeing an evidence-base for interagency work, and describe some of the challenges this poses for practitioners and service planners. We use current literature to outline the barriers and facilitators to good multi-agency practice and explore the outcomes of integrated professional work with children and young people, the development of "comprehensive CAMHS" positions, and CAMH work as an exemplar of a multi-agency service.