This book constitutes the thoroughly refereed post-conference proceedings of the Third International ICST Conference on Networks for Grid Applications, GridNets 2009, held in Athens, Greece, in September 2009. The 10full papers, 3 invited papers and 2 invited keynotes address the whole spectrum of Grid networks and cover various topics such as authorisation infrastructure for on-demand Grid and network resource provisioning, access control requirements for Grid and cloud computing systems, business models, accounting and billing concepts in Grid-aware networks, multiple resource scheduling in e-science applications, percolation-based replica discovery in peer-to-peer grid infrastructures, GridFTP GUI, alarms service for monitoring multi-domain Grid n...