To evaluate the reliability and validity of a semistructured measure of obsessive-compulsive symptom severity in children and adolescents with obsessive-compulsive disorder (OCD).

Sixty-five children with OCD (25 girls and 40 boys, aged 8 to 17 years) were assessed with the Children's Yale-Brown Obsessive Compulsive Scale (CY-BOCS). Interrater agreement was assessed by four raters in a subsample (n = 24). Discriminant and convergent validity were assessed by comparing CY-BOCS scores to self-ratings of depression, anxiety, and obsessive-compulsive symptoms.

Internal consistency was high, measuring .87 for the 10 items. The intraclass correlations for the CY-BOCS Total, Obsession, and Compulsion scores were .84, .91, and .66, suggesting good to excellent interrater agreement for subscale and total scores. The CY-BOCS Total score showed a significantly higher correlation with a self-report of obsessive-compulsive symptoms (r = .62 for the Leyton survey) compared with the Children's Depression Inventory (r = .34) and the Children's Manifest Anxiety Scale (r = .37) (p = .02 and .05, respectively).

The CY-BOCS yields reliable and valid subscale and total scores for obsessive-compulsive symptom severity in children and adolescents with OCD. Reliability and validity appear to be influenced by age of the child and the hazards associated with integrating data from parental and patient sources.