Psychiatric disorders were assessed according to standard diagnostic criteria using the structured instrument, the Diagnostic Interview for Children and Adolescents. As expected, results revealed a high rate of conduct disorder (91 percent) in both drug abusing and nondrug-abusing juvenile offenders. However, significantly higher rates of attention deficit disorder and aggressive subtype of conduct disorder were present in the offenders who abused drugs and alcohol. Excluding all conduct and oppositional disorder diagnoses, 39 percent of drug abusers versus 14 percent of those who did not abuse drugs demonstrated concurrent psychiatric diagnoses. These findings suggest that careful psychiatric evaluation of juvenile drug users may be necessary to produce optimal treatment planning. Tables and 38 references (Author abstract modified)