This book examines critical issues in classification and definition of learning disabilities; the development of theory in learning disabilities; the development of cognitive, developmental, and educational models of learning disabilities; and social and public policy in learning disabilities. After an introductory chapter by G. Reid Lyon and Louisa Moats, the book is divided into four sections. Part I covers classification of learning disabilities, including: "Models of Classification as Related to a Taxonomy of Learning Disabilities" (Roger Blashfield); "Classification of Learning Disabilities: Relationships with Other Childhood Disorders" (Jack Fletcher, et al.); "Broadening the Scope of Classification Research: Conceptual and Ecological Perspectives" (Deborah Speece); and"Issues in Empirical versus Clinical Identification of Learning Disabilities" (Robin Morris). Part II, Definition and Theory in Learning Disabilities, includes: "Defining Learning Disabilities: A History of the Search for Consensus" (John Doris); "Development of Operational Definitions in Mental Retardation: Similarities and Differences with the Field of Learning Disabilities" (Donald MacMillan); "Variations on Theory in Learning Disabilities" (Joseph Torgesen); and "A Science and Theory of Learning Disabilities" (Kenneth Kavale). Part III, Perspectives on Research and Clinical Practice in Learning Disabilities, includes the following: "Learning Disabilities from the Perspective of Cognitive Psychology" (H. Lee Swanson); "Learning Disabilities: An Interactive Developmental Paradigm" (Melvin Levine, et al.); "Learning Disabilities from an Educational Perspective" (Naomi Zigmond); and "The Construct Validity of Discrepancy Definitions of Reading Disability" (Keith Stanovich). A final section examines the impact of social and policy issues on learning disabilities, including: "Linking Purpose and Practice: Social-Political and Developmental Perspectives on Classification" (Barbara Keogh); "Learning Disabilities and Public Policy: Myths and Outcomes" (Edwin Martin) and "Conclusions and Future Directions" (Duane Alexander, et al.). Papers include references. (PB)