Reading and writing are highly valued cultural activities in our societies; therefore, a lot of time and energy are invested in teaching them to children. Although a large share of the school-age population acquire them relatively quickly, a subset of children (approximately 4 to 12 percent) experience severe difficulties in reading and spelling acquisition despite normal intelligence, normal perception, and adequate education, with effects that are persistent and difficult to treat. These children suffer from developmental dyslexia, one the most prevalent learning disabilities. In this entry the cognitive, cerebral, genetic, and environmental bases of the disorder are described, and the possible links connecting all these levels are highlighted. On top of the expected benefits for the diagnosis and the remediation of dyslexic children, research on developmental dyslexia promises to shed some light on the complex causal chains among specific genetic, neural, and cognitive factors that contribute to language development.