To determine the prevalence of DSM-IV psychiatric disorders in a representative sample of children and adolescents living in Santiago, Chile, as part of a national sample.

subjects from 4 to 18 years of age were selected in an aleatory stratified multistage fashion. As part of a national sample, 10 counties in Santiago were selected, then blocks, homes and the child or adolescent to be interviewed. Psychology graduate students applied the Spanish computer version of DISC-IV, as well as a questionnaire on family risk factors, socioeconomic index and service use.

a sample of 792 children and adolescents was evaluated, obtaining 76.7% of participation. Using the most stringent impairment algorithm, the prevalence for any psychiatric disorders was 25.4%, being 20.7% in boys and 30.3% in girls, mainly explained by anxious and affective disorders. Prevalence was higher in the 4-11 years of age than in the 12-18 (31.9% and 18.2% respectively). This difference was mainly accounted for by disruptive disorders. Prevalence of anxious disorders was the highest, but less associated with impairment, while most of the children and adolescents with affective disorders were impaired.

prevalence of psychiatric disorders in Santiago is high in this age group, and this study will be used for improving mental health services.