In the context of an evaluation of a national demonstration program for youth addiction treatment in Chile, a sociodemographic and substance use profile of children and adolescents accessing services through this new program was developed. Information regarding sociodemographic factors, substance use, and problem severity; services used; and unmet needs was retrospectively gathered for all clients (685) admitted between January 1 and June 30, 2006. Thirty-two treatment centers (91.4%) provided data. The client population profile reflected severe psychosocial circumstances (e.g., 61.4% early exit from school). Of the population, 64.9% were classified in the highest substance risk level. The primary drug reported was cocaine-paste-base (52.7%). Comparisons to similar data in other countries illustrate the more severe profile of this Chilean treatment sample. The results suggest the need for increased outreach and comprehensive intersectoral approaches. Monitoring and evaluation should become part of the culture of the national drug treatment system in Chile and other countries. (C) 2011 Elsevier Inc, All rights reserved.