This study concerns a prospective, longitudinal investigation of children with schizophrenic mothers, schizophrenic fathers, and two schizophrenic parents. As groups, these children are known to be at high risk for the eventual manifestation of schizophrenia. Prospective studies may therefore examine antecedent conditions and the pathogenic process relating to the development of the disorder prior to overt onset and without confounding by the effects and concomitants of the psychotic state. Long-term goals of this research are directed toward analyses of biological-environmental interactions, toward development of screening methods for early identification of vulnerable children, and toward instrumentation of preventive intervention programs based on a more firm understanding of etiological factors and the premorbid state. Emphasis will be placed on measures relating to possible neurophysiological dysfunctions. Attention will be given to factors that differentiate vulnerable and resistant children within the high-risk groups. The subjects in this study will be 147 children with one schizophrenic parent, 33 children with two schizophrenic parents, 65 children whose parents have non-schizophrenic disorders and 213 children whose parents are not psychiatrically ill. The age range of these children upon initial examination is 7 - 12 years. All of the children will have been examined at least twice by completion of the study. In addition, developmental data are to be collected on approximately 106 younger siblings; psychiatric evaluations will be conducted with approximately 166 older siblings of the study children.