This booklet provides an overview of the causes, symptoms, and incidence of obsessive-compulsive disorder (OCD) and addresses the key features of OCD, including obsessions, compulsions, realizations of senselessness, resistance, and shame and secrecy. Research findings into the causes of OCD are reviewed which indicate that the brains of individuals with OCD have different patterns of brain activity than those of people without mental illness or with some other mental illness. Other types of illness that may be linked to OCD are noted, such as Tourette syndrome, trichotillomania, body dysmorphic disorder and hypochondriasis. The use of pharmacotherapy and behavior therapy to treat individuals with OCD is evaluated and a screening test for OCD is presented, along with information on how to get help for OCD. Lists of organizations that can be contacted and related books on the subject are also provided. Case histories of people with OCD are included in the margins of the booklet. (Contains 11 references.) (CR)