Juvenile crime imposes enormous costs on victims, on society, and on juvenile offenders themselves. However, research assessing the efficacy of interventions for young offenders show, on average, only small effects on recidivism, substance abuse, and other behavioral outcomes. A major problem with existing interventions is that they tend to neglect individual differences in motivation and readiness to make positive changes. In earlier research, we used an empirically validated model of behavior change, the Transtheoretical Model (TTM, the "stage" model), and expert system technology to develop the Rise Above Your Situation program (RAYS), a prototype of a multimedia computerized tailored intervention designed as an adjunct to traditional juvenile justice programs. The intervention delivers assessments and individualized feedback matched to readiness to stay out of trouble with the law and quit alcohol and drugs. At the end each session the program also generates a helpgiver report that summarizes the youth's feedback and presents concrete, easy-to-implement strategies helpgivers can use to reinforce stage-matched concepts. In the current research, the goals are to complete development of the computerized tailored intervention; develop training and other support materials for helpgivers; and assess the efficacy of the intervention package in a randomized clinical trial involving 700 medium- to high-risk court-involved juveniles aged 13-17 recruited by 54 probation officers randomly assigned to treatment or standard care. Primary outcomes will be criminal recidivism and substance abuse abstinence at 6 and 12 months follow-up.