We know networks matter. However, beyond the hype, there still remains limited systematic understanding of when, why and how they function best for policy impact in international development. The objective of this paper is to review and synthesise existing literature in an effort to start to answer these questions. Reflecting broader trends, researchers in the field of civil society and international development have started to give considerable attention to networks - from transnational advocacy networks to global public policy networks (Stone and Maxwell, 2004; Keck and Sikkink, 1998). Our understanding of both subjects is as yet patchy and unsure. This paper draws together over 100 diverse texts, hoping to provide a systematic overview of this recent work from the general literature as well as from that focusing on international development. An accompanying annotated bibliography provides more information on each of the sources reviewed.