This manual, the 10th edition of a regularly published definition and classification work on mental retardation, presents five key assumptions upon which the definition of mental retardation is based and a theoretical model of five essential dimensions that explain mental retardation and how to use the companion system. These dimensions include intellectual abilities, adaptive behavior, participation, interactions, and social roles, health, and context. The volume then presents a framework for diagnosing and classifying mental retardation and planning supports. Taking advantage of 10 years of experience and feedback from the field, this new system more closely integrates the theoretical models with practical needs, thus making the new system more useful, integrated, and compatible with other classification systems. Specifically, the chapters address: (1) definition, theoretical model, framework for assessment and operational definitions; (2) the evolution of the definition of mental retardation; (3) multidimensionality of mental retardation (4) assessment of intelligence; (5) assessment of adaptive behavior; (6) diagnosis and clinical judgment; (7) classification systems; (8) etiology and prevention; (9) supports and their application to people with mental retardation; (10) physical and mental health; (11) public responsibility in the provision of supports; and (12) implications of the 2002 system. This classification system integrates theory with practical needs, including case studies and activities, which make it more useful, integrated, compatible with other classification systems. The 10th edition of this publication is an indispensable resource for everyone with an interest in mental retardation. (Contains more than 225 references.) (CR)