Recent studies have focused on reading and writing disabilities among inmates in prisons and at juvenile institutions. Some studies in Sweden have demonstrated that more than half of the delinquents have serious reading difficulties, and for immigrants the situation is even worse. However, these studies have focused on small groups. Furthermore, little attention has been paid to different types of reading and writing difficulties. The main purpose of this investigation was to estimate the prevalence of reading and writing disabilities in juvenile institutions. The study analyses gender differences and differences between immigrants and Swedish pupils. The study included 163 pupils from 22 institutions and used three tests of literacy skills: word identification, spelling and reading comprehension. More than 70% showed some problems in reading and spelling. However, only 11% had serious difficulties. Moreover, the results showed that comprehension ability among immigrant boys was lower than among Swedish boys, despite the same level of word reading skill. The high prevalence of reading and writing disabilities seems primarily to be related to social and cultural factors, home backgrounds, limited school attendance and poor self-esteem rather than to constitutional problems of a dyslexic nature. The implication of this conclusion may be important for the intervention process.