Adolescent drug use must be conceptualized within a theoretical model that includes peer, family, and intrapersonal and interpersonal factors. Risk factors associated with adolescent drug use can also be grouped into three categories: biological, psychological, and sociocultural. An increase in the number of risk factors increases the probability of drug use or drug abuse. In addition, different clusters of risk factors may have different effects on different youths and different drugs. Clinicians also need to assess potential protective factors that reduce the probability of drug use. The crucial factor in successful treatment is a complete psychosocial assessment, the establishment of appropriate and attainable goals, and the use of all community resources indicated by the assessment and treatment plan. No generic approach fits all youth; the clinician needs to design the treatment plan specifically for the individual client. Further research is needed regarding outcomes of treatment matching protocols and prevention and intervention strategies. Case examples and 27 references