This chapter reviews the current state of knowledge regarding the phenomenology, diagnosis, etiology, and treatment of obsessive-compulsive disorder (OCD) specifically as related to children and adolescents. The most common compulsions seen include excessive washing or cleaning, repeating, checking, touching, counting, ordering/arranging, and hoarding. Behaviors which may indicate the presence of OCD include lengthy bedtime rituals or exaggerated requests for reassurance, particularly if centered on a fear of harm coming to self or others. Additional evidence supporting a neurobiologic etiology of OCD includes a plethora of neuroanatomic, neurophysiologic, and neuroimmunologic findings. Psychodynamic psychotherapy may be an effective approach to the treatment of comorbid conditions such as depression or personality disorders (American Academy of Child and Adolescent Psychiatry, 1998). In conclusion, CBT and pharmacotherapy appear to work well together, and many children with OCD require or would benefit from both CBT and pharmacotherapy.