The pediatrician has at his or her disposal a highly accurate and reliable system of drug testing to provide additional information relevant to substance abuse in children and adolescents. As always, the judgments engendered in questions such as when it is ethical to order such tests, the confidentiality of the results, and how to integrate such findings into the overall management of the patient and his or her family are much more important and problematic than the technical aspects of testing. In selected clinical situations, however, drug testing can provide reliable and useful information and is indicated in the diagnosis and management of substance abuse in adolescents.