This application is for continued support of the administrative and research cores of the UCLA Mental Retardation Research Center. This MRRC was first established in 1969 and housed with Child Psychiatry in a four floors addition to the Neuropsychiatric Institute. This MRRC provides a comprehensive multi-disciplinary in the field of mental retardation and developmental disabilities (MRDD). The research investigations carried out by the Center Investigators address most of the MRDD research priorities listed in the current RFA issued by National Institute of Child Health and Human Development (NICHD) for MRDD Research Centers. The long-term goals of the Center are to discover ways to prevent mental retardation and improve the quality of life for mentally retarded and other developmentally disabled individuals. To accomplish this, five multi- disciplinary research groups have been organized: Clinical Research, Molecular and Developmental Neuroscience Neurobiochemistry and Molecular Genetics, Systems Neuroscience and Socio-behavioral Research. To foster research excellence and innovation through inter- disciplinary interactions among investigators. An Administrative Core and eight research cores have been organized: (1) Molecular Biology, (2) Cell Biology, (3) Neurocytology and Cellular Imaging, (4) Animal Maintenance and Assessment, (5) Field Work Training and Outcome, (6) Data Management and Analysis, (7) Microcomputers and/Media Graphics and (8) Technical Services. The essential scope and mission of the Center are to elucidate the molecular, cellular and behavioral mechanisms underlying the pathogenesis of MRDD and to translate this fundamental knowledge into novel diagnostic, preventive and therapeutic approach which ultimately an be applied to clinical care. The function of the Center is to provide an environment promoting the highest level of research in mental retardation at UCLA by fostering interaction among investigators and providing free access to cutting edge and efficient core services. The Center assigns high priority to the support of talented young investigators and the training of pre- and post-doctoral fellows in a variety of disciplines related to its goals.