The aim of this study was to describe the history, factor structure and psychometric properties of the Children's Automatic Thoughts Scale (CATS). The CATS is a self-report measure designed to assess a wide range of negative self-statements in children and adolescents. The results of confirmatory factor analyses supported four distinct but strongly correlated factors relating to automatic thoughts on physical threat, social threat, personal failure and hostility. The internal consistency of the total score and subscales was high and test-retest reliability at 1 and 3 months was acceptable. The CATS effectively discriminated between control children and adolescents, and clinically anxious, depressed, or behavior disorder children and adolescents, and showed good discriminant validity across clinical subgroups on the subscales. Results suggest that the CATS is a promising instrument in the assessment of a range of negative automatic thoughts across both internalizing and externalizing problems in young people.