Many dyslexics manage to partly compensate for their difficulties to reach the lower normal range of reading ability. At the same time, psycholinguistic experiments show that their phonological deficit perdures in a qualitatively similar form throughout their life, evidencing very limited plasticity. I will present new experiments exploring the nature of the phonological deficit and further confirming its persistence in dyslexic adults. I will then discuss neurobiological data in search of insights into the reasons for such a remarkable absence of plasticity.