The objectives of this study (done at the Psychiatric Clinic of the Karolinska Institute, Stockholm, between 1947 and 1950) were to determine the possible existence of an hereditary form of specific dyslexia and through a clinical analysis to discover something about the mode of inheritance. The role of certain extraneous factors was also to be considered. The case material consisted of 79 children from the Stockholm Child Guidance Clinic diagnosed as having specific dyslexia plus 43 children from the special reading classes of a secondary school.