Background: The familial relationship between obsessive–compulsive disorder (OCD) and “obsessive–compulsive spectrum” disorders is unclear. This study investigates the relationship of OCD to somatoform disorders (body dysmorphic disorder BDD and hypochondriasis), eating disorders (e.g., anorexia nervosa and bulimia nervosa), pathologic “grooming” conditions (e.g., nail biting, skin picking, trichotillomania), and other impulse control disorders (e.g., kleptomania, pathologic gambling, pyromania) using blinded family study methodology. Methods: Eighty case and 73 control probands, as well as 343 case and 300 control first-degree relatives, were examined by psychiatrists or Ph.D. psychologists using the Schedule for Affective Disorders and Schizophrenia—Lifetime Anxiety version. Two experienced psychiatrists independently reviewed all diagnostic information and made final consensus diagnoses using DSM-IV criteria. Results: Body dysmorphic disorder, hypochondriasis, any eating disorder, and any grooming condition occurred more frequently in case probands. In addition, BDD, either somatoform disorder, and any grooming condition occurred more frequently in case relatives, whether or not case probands also had the same diagnosis. Conclusions: These findings indicate that certain somatoform and pathologic grooming conditions are part of the familial OCD spectrum. Though other “spectrum” conditions may resemble OCD, they do not appear to be important parts of the familial spectrum.