This study examines the role of family and friends in accounting for alcohol, tobacco, and marijuana use among young adolescents. The sample included 1,008 males and 1,040 females with a mean age of 14.5 years. Lack of parental affection, concern, involvement, and modeling appeared to be centralfactors in the family's influence, which accounted for up to 22% of the variance in drug use. Friends' delinquency and use of drugs largely determined the influence of friendship, which accounted for up to 40% of adolescent drug use. Comparisons are made between characteristics of family and friends. Family and friends have differing influences upon young people, and these in turn depend on chronological or biological age, culture, historical time, sex, personal characteristics, and the behavior in question. Influence as causation is difficult to demonstrate unequivocally; however, what can be shown is the extent of covariation between family or friendship characteristics and the behavior of interest. Such descriptive information is one source from which causative theories may be developed. This study concerns the extent to which drug use by young adolescents is related to characteristics of both their family and their friends. The importance of both family and friends in the prediction of drug use has been recognized for some time. However, research in this area has