Empirical evidence supports a strong relationship between drug use and delinquency, an association documented regardless of drug type, offense committed, and population sampled. Research also discloses that factors for both delinquency and drug use include family, peer and personality variables that were common predictors; low educational achievement as a common and early predictor; family structure and conflict as common variables; and childhood aggression as predictive of frequent adolescent drug use and delinquency. The chapter reviews these and other etiological factors and presents developmental progression as well as risk/protective factors as key concepts to more completely understand the relationship of drug use and delinquency. Understanding both the causes and effects of multiple pathways in and out of substance use and abuse has implications for both prevention and intervention programming. Additional research should examine biobehavioral prevention interventions, multiple interventions, the timing and sequencing of interventions, and the focusing of interventions on individual needs. Figure, references