Observed parent–adolescent autonomy struggles were assessed as potential predictors of the development of peer-rated hostility over a decade later in young adulthood in both normal and previously psychiatrically hospitalized groups of adolescents. Longitudinal, multireporter data were obtained by coding family interactions involving 83 adolescents and their parents at age 16 years and then obtaining ratings by close friends of adolescents’ hostility at age 25 years. Fathers’ behavior undermining adolescents’ autonomy in interactions at age 16 years were predictive of adolescentsas-young-adults’ hostility, as rated by close friends at age 25 years. These predictions contributed additional variance to understanding young adult hostility even after accounting for concurrent levels of adolescent hostility at age 16 years and paternal hostility at this age, each of which also significantly contributed to predicting future hostility. Results are discussed as highlighting a pathway by which difficulties attaining autonomy in adolescence may presage the development of long-term difficulties in social functioning.