The fundamental theorem of primary socialization theory is that normative and deviant behaviors are learned social behaviors, products of the interaction of social, psychological, and cultural characteristics, and that norms for social behaviors, including drug use, are learned predominantly in the context of interactions with the primary socialization sources. During adolescence, learning of social behaviors is frequently dominated by interactions with peer clusters. There are a number of additional postulates: 1) The strength of the bonds between the youth and the primary socialization sources is a major factor in determining how effectively norms are transmitted. 2) Any socialization link can transmit deviant norms, but healthy family and school systems are more likely to transmit prosocial norms. 3) Peer clusters can transmit either prosocial or deviant norms, but the major source of deviant norms is usually peer clusters. 4) Weak family/child and/ or school/child bonds increase the chances that the youth will bond with a deviant peer cluster and will engage in deviant behaviors. 5) Weak peer bonds can also ultimately increase the changes of bonding with deviant peers. Primary socialization theory is consistent with current research, has strong implications for improving prevention and treatment, and suggests specific hypotheses for further research.