This validation study assessed the degree of confidence that can be placed on inferences from depressive symptoms among adolescents, based on a 12-item version of the Centre for Epidemiological Studies Depression scale (CES-D). This short version of the scale had been developed for application in the National Longitudinal Study of Children and Youth and we refer to it as the CES-D-12-NLSCY. The major data source for the present validation study was a 2002/2003 survey of 12,990 students in junior and senior high school in the Atlantic provinces of Canada. Receiver operating characteristic curve analyses for two different proxy gold standards yielded adequate areas under the curve (AUCs) of .84 and .80, allowing us to establish cut points for three categories of depressive symptoms in the general adolescent population: Minimal (CES-D-12-NLSCY total score 0 to 11), Somewhat Elevated (total score 12 to 20) and Very Elevated (total score 21 to 36). The CES-D-12-NLSCY was found to have acceptable internal consistency (Cronbach=s alpha .85). All but one of the 12 items of the CES-D-12-NLSCY were found to have acceptable discrimination ability. The prevalence of Minimal, Somewhat and Very Elevated depressive symptoms in the adolescent student population of the Atlantic provinces was estimated to be 72.3, 19.5 and 5.5 percent, respectively. A further 2.6 percent of students who responded to fewer than 11 items of the scale were classified as Indeterminate with regards to depressive symptom category. The major threat to the accuracy of the CES-D-12-NLSCY is its lack of inquiry about irritability, which is a key symptom of depression in youth.