This workshop describes assessment and cognitive-behavioral treatment of obsessive-compulsive disorder in children. Dr. Piacentini begins by describing the diagnostic criteria for OCD and how the symptoms manifest in childhood. He describes how triggers and negative reinforcement contribute to the obsessive-compulsive cycle that maintains OCD. Assessment tools presented include behavioral assessment tasks and the Children's Yale-Brown Obsessive Compulsive Scale. In addition, Dr. Piacentini summarizes the importance of family environment during treatment and provides guidance on selecting a treatment strategy. Lastly, he demonstrates a treatment session through role play.