Research in etiology, neurobiology, genetics, clinical correlates, and evidence-based treatments in children and adolescents with obsessive-compulsive disorder indicate a need for the revision of the Practice Parameters for the Assessment and Treatment of Children and Adolescents with Obsessive-Compulsive Disorder first published a decade ago. The present article highlights the clinical assessment and reviews and summarizes the evidence base for treatment. Based on this evidence, specific recommendations are provided for assessment, cognitive behavioral therapy, pharmacotherapy, combined treatment, and other interventions. (Contains 1 table.)