Obsessive-compulsive disorder (OCD), despite our increasing understanding of its causes and its effective treatment, remains a chronic and underdiagnosed disorder. Both treatment with SSRIs and the behavioral treatment strategy of exposure with response prevention have been proved by clinical trials to be effective and safe in treating OCD; however, even these treatments sometimes elicit only moderate patient response, and some OCD patients do not respond to them at all. Preliminary data suggest that OCD has lifelong persistence and that discontinuation of pharmacotherapy often leads to relapse. Nonetheless, further prospective, controlled, maintenance studies of OCD are needed to determine factors in and predictors of recovery, remission, and relapse. Finally, new procedures for treatment-refractory patients are needed; neurosurgical and new pharmacologic approaches have shown promise in treating these patients and should be studied in controlled trials.