Child psychiatric disorders are common and treatable, but often go undetected and therefore remain untreated. To assess the Strengths and Difficulties Questionnaire (SDQ) as a potential means for improving the detection of child psychiatric disorders in the community, SDQ predictions and independent psychiatric diagnoses were compared in a community sample of 7984 5-15 year olds from the 1999 British Child Mental Health Survey. Multi-informant (parents, teachers, older children) SDQs identified individuals with a psychiatric diagnosis with a specificity of 94.6% (95% Cl, 94.1-95.1%) and a sensitivity of 63.3% (59.7-66.9%). The questionnaires identified over 70% of individuals with conduct, hyperactivity, depressive, and some anxiety disorders, but fewer than 50% of individuals with specific phobias, separation anxiety and eating disorders. Sensitivity was substantially poorer with single-informant rather than multi-informant SDQs. Community screening programmes based on multi-informant SDQs could potentially increase the detection of child psychiatric disorders, thereby improving access to effective treatments.