Purpose: To determine the prevalence of substance use among adolescent psychiatric outpatients using a variety of data sources. Method: Using a questionnaire, 3-month prevalence of substance use data were obtained from 50 adolescents and their health care providers. Adolescents' self-reports and providers' clinical impressions were compared with urine screen results. Results: The prevalence of substance use was low with the exception of self-reported cannabis and alcohol use, 48% and 70%, respectively (N=50). Conclusion: Urine screening did not provide extra information on adolescent psychiatric outpatients' substance use compared to patients' self-reports and health care providers' clinical impressions.