Following a clear introduction to what local development is and why it is significant, this chapter outlines the importance of effective organisational arrangements for the planning and delivery of local economic development, and of the particular role that development agencies can play. Through a review of the literature the case is made that, despite their proven success and growing prevalence, understanding and appreciation of these flexible, innovative and pragmatic tools for local development are less than what they should be. The chapter concludes suggesting that by drawing on a core evidence base of case studies of 16 agencies in 13 local economies to answer a number of key questions the publication will review how development agencies have contributed as leaders in the local development system.