The diagnosis of 'Dyslexia' and the medical problematisation of reading difficulties were almost unknown one hundred years ago, yet today the British Dyslexia Association estimates that up to ten per cent of the UK population may have some form of dyslexia, with numbers in the United States estimated to be as high as twenty per cent. The Government of Reading investigates how this problematisation developed and how a diagnostic category was shaped in response to this.