These proceedings of the NATO Advanved Study Institute on Differential Diagnosis and Treatments of Reading and Writing Disorders aim to answer the following questions, from their different research programs: What is the nature of differential diagnosis of reading disabilities?; Are intelligence test scores relevant?; How important is pseudoword reading?; What about listening comprehension?; How best can clinicians supplement group results with individual developmental profiles of reading and writing skills?; How do different models of language-related components within a cognitive-developmental framework explain individual differences in reading disabilities?; What is the nature of phonemic awareness, phonological awareness within the broad context of phonological processing in children with reading disabilities?; What are the differential strategies of poor readers/spellers?.