Over the past century, body dysmorphic disorder (BDD), a preoccupation with an imagined or slight defect in appearance, has been hypothesized to be related to obsessive-compulsive disorder (OCD). More recently, BDD has also been hypothesized to be a form of affective spectrum disorder. Affective spectrum disorder refers to a family of disorders postulated to have a common pathophysiologic abnormality. This grouping of disorders has been identified on the basis of their response to pharmacologic treatments and is supported by comorbidity and family studies. Available data suggest that BDD should be considered a candidate form of affective spectrum disorder--a disorder that may eventually be demonstrated to belong to this family of disorders. Available data also strongly support the hypothesis that BDD is an obsessive-compulsive spectrum disorder. Because OCD itself has been hypothesized to be an affective spectrum disorder, BDD may be more narrowly conceptualized as an obsessive-compulsive spectrum disorder and more broadly as a candidate form of affective spectrum disorder.