The thesis of this study is that children and adolescents who grow up in intact families are generally less likely to smoke, to drink, or to try illegal drugs than children and adolescents who grow up in non-intact families, which, for the purposes of this paper, are defined as single-parent families, blended or stepfamilies, and no-parent families. Using both a bivariate regression model and several multiple regression models, the paper sets out to test the hypothesis that family structure has a significant impact on the level of risk of adolescent drug use even when controlling for other factors that encourage or inhibit initiation into drug use. Further, the paper, unlike previous studies tackling this same issue, explores why family structure is important in determining drug use among adolescents. Namely, it explores the role of “”father closeness”” both in accounting for the importance of an intact family as an inhibitor of drug use, and as an important factor inhibiting drug use in its own right, independent of family structure. Previous studies have lumped the effect of mothers and fathers together, or have even entirely ignored the role of fathers. This study sets out to separate these effects, and on the way to analyzing the independent role of father closeness, the report also explores the importance of mother closeness and peer influence on adolescent drug use. (Author abstract)