Allergic diseases represent a major health problem in Europe. They are increasing in prevalence, severity and costs. GA2LEN, an FP6 Network of Excellence, was created in 2005 as a vehicle to ensure excellence in research bringing together research and clinical institutions to combat fragmentation in the European research area and to tackle Allergy in its globality. GA2LEN benefited greatly from the voluntary efforts of researchers who are strongly committed to this model of pan-European collaboration. The network was organized in order to increase networking for scientific projects in allergy and asthma around Europe and to make GA2LEN the world leader in the field. Besides these activities, research has been jointly made and the first papers are being published. GA2LEN achievements in general can be grouped as those for a durable infrastructure built up during the project phase those which are project-related work based on these novel infrastructures, and the development and implementations of guidelines. The major achievements of GA2LEN are reported in this paper.