The available literature on etiological aspects and treatment of childhood and adolescent obsessive-compulsive disorder is reviewed. Reports regarding the etiological background are still inconsistent, but there is increasing evidence of a biological background with involvement of serotonin neurotransmitter systems. It seems that a combination of medication and behavioral therapy is most effective in the treatment of OCD. Only a few controlled trials of medication in the treatment of OCD in children and adolescents have been published. Such studies, including a considerable number of patients over a considerable period of time, are still needed.