This volume is a selection of best papers presented at the CoreGRID - tegration Workshop 2006 (CGIW’2006), which took place on 19–20 October 2006 in Krakow, Poland. The workshop was organised by the Network of Excellence CoreGRID funded by the European Commission under the sixth Framework Programme IST-2003-2.3.2.8 starting September 1st, 2004 for a duration of four years. CoreGRID aims at strengthening and advancing scienti?c and technological excellence of Europe in the area of Grid and Peer-to-Peer technologies. To achieve this objective, the network brings together a critical mass of we- established researchers from forty institutions who have constructed an - bitious joint programme of activities. The goal of the workshop is to promote the integration of the CoreGRID network and of the European research community in the area of Grid and P2P technologies, in order to overcome the current fragmentation and duplication of efforts in this area. The list of topics of Grid research covered at the workshop included but was not limited to: knowledge and data management; programming models; system architecture; Grid information, resource and work?ow monitoring services; resource management and scheduling; systems, tools and environments; trust and security issues on the Grid. Priority at the workshop was given to work conducted in collaboration between partners from different research institutions and to promising research prop- als that can foster such collaboration in the future.