In this paper we consider a complex of language-related problems that research has identified in children with reading disorder and we attempt to understand this complex in relation to proposals about the language processing mechanism. The perspective gained by considering reading problems from the standpoint of language structure and language acquisition allows us to pose specific hypotheses about the causes of reading disorder. The hypotheses are then examined from the standpoint of an analysis of the demands of the reading task and a consideration of the state of the unsuccessful reader in meeting these demands. The remainder of the paper pursues one proposal about the source of reading problems, in which the working memory system plays a central part. This proposal is evaluated in the light of empirical research which has attempted to tease apart structural knowledge and memory capacity both in normal children and in children with notable reading deficiencies.