Survey data indicate that more than half of all high school seniors have tried at least one illegal drug, and nearly half have tried cannabis or marijuana; nearly one in four teens has tried drugs other than marijuana. Clearly, the justice system cannot afford the time and resources that would be required to process in juvenile drug courts all adolescent substance users because they happen to be arrested. Limited resources thus require that there be a screening process governed by criteria that define which juvenile drug users are eligible for drug court participation. In developing such criteria, juvenile drug courts must target the youth most likely to respond positively to the intervention techniques used by the court, as well as those most likely to escalate their substance abuse to dangerous levels absent intervention. This requires a careful analysis that can reliably identify the factors likely to lead to long-term, harmful drug abuse. The youth at greatest risk of severe problems of drug use are apparently those that go beyond alcohol and marijuana to use other illegal drugs. Although all juveniles who use illicit drugs of any type have broken the law, this does not mean they all should be placed in the juvenile justice system for extended treatment and intervention. 3 tables, 6 figures, 4 notes, and 78 references