This project addresses fundamental questions about syndrome expression, developmental trajectories, and predictors of outcome in autism by examining a uniquely characterized cohort of children identified with a pervasive developmental disorder at 2 years of age. As part of their participation in the CPEA/STAART program project at Yale, the children have completed standardized as well as experimental measures in several core domains of autistic psychopathology at 2 years (Time A) and then again at 4 years of age (Time B). The current proposal targets social and neuropsychological processes and diagnostic outcome in this group of children at 8 years of age (Time C) when their presentation can be expected to be more fully expressed. The specific goals of the project are framed around developmental psychopathology principles that capitalize on a singular cohort and innovative outcome measures that we have developed to capture dimensionality in the manifestation of autistic symptomotology. The aims are to examine the relationship between (1). Early-emerging social processes measured at Times A and B, and outcome measures of communicative competence, social ability and disability, and behavioral and neurofunctional constructs at Time C; (2) Measured neuropsychological processes at Times A and B, and outcome measures of neuropsychological and social communicative abilities and disabilities (as above) at Time C; and examine whether (3) Early social and neuropsychological processes at Times A and B predict categorical diagnostic assignment at Time C. The design of this project permits both a longitudinal analysis of predictors of outcome as well as a cross-sectional examination of the relationships between social and neuropsychological processes and diagnostic status. By mapping the continuities and discontinuities of the central features of autism from first detection at two years of age to later childhood, this study is expected to help clarify syndrome expression and diagnostic pathways at the level of developmental processes as well as permit us to disentangle what leads to social disabilities from the effects of having such disabilities. The improved identification and capacity for measurement of the essential dimensions of the autism phenotype and resolution of issues related to phenotypic boundaries and diagnostic categorization is expected to inform research on the pathogenesis of autism and development of relevant treatment goals and outcome measures.