The purpose of this research is to continue our study of a group of children with abnormalities of the sex chromosomes who are identified in a cytogenetic survey of 40,000 consecutive births from 1964-1974. This patient group offers the opportunity for study of genetic, developmental, physical, and psychological factors in these complex conditions. Our long-term objective is to define the ultimate prognosis for each of these conditions--47,XXX; 47,XXY; 47,XYY; 45,X and mosaicisms of these. Some, but not all, individuals with these karyotypes will have intellectual, emotional or social problems in later life. One research aim is to develop criteria, as early as possible, for separating those children who are at significant risk from those who are not. The data will be analyzed by comparisons between sub-groups and by using normal siblings as controls. Previous study of this group of children makes it possible to focus the investigation during childhood on particular facets of vulnerability, and during adolescence on relative changes from previous growth, endocrine and behavioral status. By following the development and by therapeutic intervention, where possible, when symptoms occur, later irreversible pathology may be prevented or ameliorated. These studies should illuminate the pathological picture and the underlying normal mechanisms which are defective in these individuals. In addition, by defining the long-term prognosis of newborns with these abnormalities, the current dilemma of the patient and the physician faced with these conditions in utero will be resolved.