The paper summarizes several approaches to the identification of learning disability and then discusses the nature of learning disability in the context of competing hypotheses as possible explanations of insufficient or unsatisfactory achievement. Because learning disability may only be inferred as a cause of unsatisfactory learning, the information requirements of adequate diagnosis are postulated, and a researchable theoretical network of relationships is presented. Learning disability is seen as a breakdown either in the neurological process or a result of some physically damaging event or situation, or as an impairment of mental functioning as a result of a profound deprivation of stimulating environment. The latter alternative is seen to be highly speculative, but to afford a possible explanation of cases of disability which do not show signs of neurological impairment. The complexity of learning disability is recognized by this approach and suggestions are made for studying the phenomenon. (Author/SBH)