Our objective in this study was to compare the demographics and clinical characteristics of patients with episodic and chronic obsessive-compulsive disorder (OCD). We recruited 128 outpatients with a primary diagnosis of OCD according to DSM-IV diagnostic criteria. The episodic (n=24) and chronic (n=104) OCD patient groups were compared with respect to demographic variables and scores from various psychiatric rating scales. The severity of compulsions was found to be significantly lower in the episodic OCD group than in the chronic OCD group. When the frequency of Axis I disorders was assessed in the two groups, bipolar disorder was found to have a significantly higher prevalence rate in the episodic OCD group than that in the chronic OCD group. The results of our study point to the possibility of an association between a subgroup of OCD with an episodic course and bipolar disorder. The evidence of such a relationship, which needs to be confirmed in a larger sample, might expand the scope of the clinical assessment and therapy of this subgroup of OCD.