This volume comprises the edited proceedings of the 2006 CoreGRID Integration Workshop (CGIW'2006), held October 2006 in Krakow, Poland. A ?Network of Excellence? funded by the European Commission's Sixth Framework Program, CoreGRID, aims to strengthen and advance scientific and technological excellence in the area of Grid and Peer-to-Peer technologies by bringing together a critical mass of well-established researchers from 41 European research institutions. Achievements in European Research on Grid Systems covers, though is not limited to, the following topics: knowledge and data management; programming models; system architecture; Grid information, resource and workflow monitoring services; resource management and scheduling; systems, tools and environments; trust and security issues on the Grid. Designed for a professional audience of industry practitioners and researchers, Achievements in European Research on Grid Systems is also suitable for advanced-level students in computer science.