This is an application to extend the NICHD Study of Early Child Care and Youth Development (SECCYD) into its fourth phase. The SECCYD is a collaborative, prospective, longitudinal study of a cohort of 1,073 adolescents and their families, first enrolled at one month of age and studied intensively through sixth grade in Phase lll of this cooperative agreement. The primary study aims of Phase IV are (1) to investigate how earlier functioning and experiences, in concert with contextual and maturational factors in adolescence, influence social relationships, health, adjustment, and intellectual and academic development during middle adolescence; and (2) to extend into middle adolescence an intensive and extensive study of patterns of health and human development from infancy onward, which can be used by the broader scientific community to study a wide range of basic and applied questions. Primary data collection in Phase IV occurs when the adolescents are 15 years old, and again, at 16. At 15, a home visit occurs in which parent-adolescent interactions are videotaped and the adolescents and their parents (or parental figures) complete questionnaires and structured interviews. During lab visits at ages 15 and 16, adolescents' achievement is assessed and adolescents complete self-report measures. The age 15 data collection also includes an extensive assessment of the adolescent's cognitive functioning, cortisol reactivity, and physical activity. In addition, yearly examinations of pubertal status and health are conducted. Finally school personnel complete questionnaires and adolescents' school transcripts are coded at the end of middle school and Grade 10. These data, in concert with data from earlier Phases, will be used to test four models of developmental processes. [unreadable] [unreadable] [unreadable]