Those who design substance-use prevention programs and those who evaluate them must be aware of the multiple goals of primary prevention: to anticipate problems, to reduce the number of new cases, to promote competencies that protect against the development of problems, and to encourage optimal health. Intervention at the level of the individual is not sufficient. Programs must not only involve multiple levels of intervention for individuals, but also include assessments of the larger social context in which drug abuse occurs. To be effective, programs must reach both high-risk and normal-risk youth. Programs that include community-level components are apparently the most effective for high-risk youth, and programs based in skills training and social-norm-changing seem to work with normal-risk youth. Social norms regarding substance use may be more salient than the ability to resist pressure to use substances. This is shown by the fact that the majority of the programs have not been able to affect alcohol use, and when skills have been measured for their impact on substance use, there has been no impact for resistance skills. Conceptualizations regarding the relationship between youth and drugs must be expanded beyond models that assume the reasons youth use drugs are because they do not have enough information, and they are pressured to use drugs. Future programs should explore the rewarding role that drugs may play in the lives of juveniles and develop ways to make incompatible alternatives desirable. Programs must also explore the factors that make certain youth at risk for drug-related problems. Implementation evaluation can be improved through steps such as assessing comparison groups and obtaining information on how programs are implemented at various sites. Causal mediating variables should be assessed as well. Currently, information is not available on how well various programs work with different populations; such information could be important to decisionmakers. Evaluators must replace simplistic models of change with complex models that address the realities of substance use by adolescents. 47 references