Two symptom clusters within the obsessive-compulsive (OC) spectrum - the impulsive cluster and the schizo-obsessive cluster - are discussed in this paper. Disorders characterized by impulsivity include disorders of impulse control (eg, intermittent explosive disorder, pyromania, kleptomania, pathologic gambling, trichotillomania); paraphilias, sexual impulsions, and sexual addictions; and impulsive aggression personality disorders (eg, borderline, antisocial, histrionic, and narcissistic personality disorders). The schizo-obsessive cluster includes comorbid symptoms of obsessive- compulsive disorder (OCD) and schizophrenia. Both clusters of disorders have a substantial impact on individuals and society. This article examines the overlap of symptoms between OCD and OC spectrum disorders, along with possible treatment options. Studies on the effectiveness of serotonin reuptake inhibitors in treating pathologic gambling, compulsive buying, and comorbid OCD and schizophrenia are presented. The need for additional large scale, adequately-controlled studies is discussed.