Summary: The purpose of the present study was to investigate the gender-related differences of clinical features in a sample of obsessive-compulsive (OCD) patients. One hundred and sixty outpatients with a principal diagnosis of obsessive-compulsive disorder (DSM-IV, Y-BOCS = 16) were admitted. Patients were evaluated with a semi-structured interview covering the following areas: socio-demographic data, Axis I diagnoses (DSM-IV), OCD clinical features (age at onset of OC symptoms and disorder, type of onset, life events and type of course). For statistical analysis the sample was subdivided in two groups according to gender. We found an earlier age at onset of OC symptoms and disorder in males; an insidious onset and a chronic course of illness were also observed in that group of patients. Females more frequently showed an acute onset of OCD and an episodic course of illness; they also reported more frequently a stressful event in the year preceding OCD onset. A history of anxiety disorders with onset preceding OCD and hypomanic episodes occurring after OCD onset was significantly more common among males, while females showed more frequently a history of eating disorders. We found three gender-related features of OCD: males show an earlier age at onset with a lower impact of precipitant events in triggering the disorder; OCD seems to occur in a relative high proportion of males who already have phobias and/or tic disorders; and a surfeit of chronic course of the illness in males in comparison with females.