22,750,000 dyslexic individuals, including 2,500,000 dyslexic school children in the EC have a specific disorder in learning to read and spell (dyslexia). So far the etiology of dyslexia is poorly understood. Therefore, it is mandatory to tackle the problem from several directions. In a multicentre, multidisciplinary project we will investigate the biological basis of dyslexia by collecting powerful samples of subjects consistently characterised across EC populations on three different levels: genetics, environment, and neuroscience.