The aim of this paper is to evaluate the effectiveness of brief interventions (BI) with adolescents (mean age <20) in reducing alcohol, tobacco or other drug (ATOD) use by means of a systematic review of BI for adolescent substance use in the English language literature up to 2002. We identified 11 studies involving 3734 adolescents. Follow-up ranged from 6 weeks to 24 months. Motivational interviewing was the predominant approach, underpinning eight studies: the remaining three provided personalized health information. Seven papers reported outcomes for alcohol interventions and four involved other substances (including one with separate alcohol outcomes). The overall effect size was d=0.126 with borderline homogeneity (Q=14.9, df=9, p=0.09). The effect size from the eight alcohol interventions (n=1,075) was classified as significant but "small" (d=0.275). The remaining non-alcohol studies were considered separately as interventions involving tobacco or multiple substance use. The two interventions with tobacco involved a substantial sample (n=2,626) but had a very small effect (d=0.037), while the two interventions addressing multiple substances involved few participants (n=110) but had a medium-large effect (d=0.78). Across a diverse range of settings (dental clinic, schools, universities, substance treatment centres) and, therefore, probably diverse clients, BI conferred benefits to adolescent substance users. BI had a small effect on alcohol consumption and related measures. The data for tobacco interventions suggested a very small reduction, particularly with general community interventions. The effect of BI with multiple substances appears substantial but the small sample cautions against expansive generalization.