The purpose of the present paper was to identify the rate of prevalence of impulse control disorders (ICD) in patients with obsessive-compulsive disorder (OCD) and to compare patients with OCD with and without ICD with regard to sociodemographic, clinical and prognostic characteristics. Forty-five patients with OCD were assessed by means of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (4th edn, DSM-IV) plus additional modules for the assessment of ICD and examined using the Yale-Brown Obsessive-Compulsive Scale, the Clinical Global Impression, the Beck Depression Inventory, the Hamilton Depression Rating Scale, and the Global Assessment of Functioning. These patients were treated with serotonin reuptake inhibitors (SRI) and followed for a variable period of time. Individuals with ICD (here defined as including not only the impulse control disorders not elsewhere classified of the DSM-IV, but also other disorders in which impulse control is a prominent feature such as alcohol and drug dependence, paraphilias and bulimia nervosa/binge eating disorder) were compared to those without ICD using the Mann-Whitney U-test and the Pearson's goodness of fit chi(2) test. Sixteen patients with OCD (35.5%) displayed comorbid ICD. Patients with ICD were characterized by a significantly earlier age at OCD onset (P = 0.04), a more insidious appearance of OCD symptoms (P = 0.04), a higher rate of comorbid anxiety disorders (P = 0.03), a greater number (P = 0.02) and severity of compulsive symptoms (P = 0.04), an increased rate of counting compulsions (P = 0.02), and a higher number of required SRI trials (P = 0.01). When OCD is found in association with ICD, the clinical picture is characterized by a greater severity of the obsessive-compulsive symptoms at presentation and by the requirement of a greater number of therapeutic attempts during follow up.