This study examined the interrelationships between individual development and the family system by testing the hypothesis that variations in family relations during middle adolescence are associated with psychological and social aspects of adolescent development and with parental midlife development. Data were collected from 27 parent-adolescent triads (mothers, fathers, adolescents) through individually mailed questionnaires. Measures of adolescent development included psychosocial maturity and adult role behavior. Parental midlife development was assessed by marital quality and midlife transition scales. Measures of family dynamics included assessments of family adaptability/cohesion, and communication as reported by each member of the triad. All measures had demonstrated reliability and validity. The results indicated that adolescents' and parents' reports about the parent-adolescent relationship and family functioning corresponded to their own internal and behavioral development. For example, parents perceived less optimal family functioning as their adolescent assumed more behavioral, but not more psychological maturity. In addition, parents with higher midlife crisis scores reported lower parent-adolescent communication scores. The results highlight the utility of using the family systems approach to understand adolescent and adult development and parent-adolescent relationships. (Author)