Using an integration of social control theory and the routine activity perspective, adolescent time use was examined for effects on problem behaviors. We examined a wide variety of time use categories, including homework, extracurricular activities, sports time, alone time, paid work, housework, television watching, as well as indices of family time and peer time, for their effects on heavy alcohol use, cigarette smoking, illicit drug use, delinquency and sexual activity. The study employed a representative household sample of adolescents (n = 606) and took into account important sociodemographic factors--gender, age, race (Black and White), and socioeconomic status. The most important predictors of adolescent problem behaviors were family time and peer time. Family time serves as a protective factor against all five problem behaviors while peer time is a highly significant risk factor for all five problem behaviors.