In this assignment I look at developmental dyslexia and the research and empirical studies done on this subject over the last several years. Developmental dyslexia is a failure to acquire normal reading skills and affects from 5 to 17,5% of schoolchildren despite adequate intelligence, education and social background. There is today agreement that dyslexia is a neurological disorder with a constitutional origin. The last decades there has been a great deal of research but there is still disagreements over the neurological and cognitive basis of the disorder. There are today four major hypotheses of dyslexia, within two different categories. The proponents of each of these hypotheses have gathered empirical evidence to support their own view. On one hand there is the phonological deficit hypothesis, which states that dyslexia is a cognitive deficit characterised by a deficit in phonological awareness, speech sound decoding and problems with verbal short time memory, and that the deficit arises form a dysfunction in cortical areas. The last years this hypotheses has got competition from three other hypotheses which agree that the outcome is a phonological deficit. But these hypotheses see it as a deficit secondary to a more basic auditory or visual impairment, or as a general cerebellar/sensorimotor deficit. Post mortem studies of brains from dyslectic persons show anomalies in multiple areas of the brain, supporting the hypotheses of a complex anatomic basis. Although there are some dyslectics who do not exhibit deficits in other areas than phonology, there is a large group of dyslectics that exhibit auditive, visual or motor impairments. The question is if these are casually connected or represent co-morbidity. It will be necessary with more research on the basis of the phonological deficit and eventually co-occurrences of phonological deficit and deficits in motor and sensory regions.