Objective: Although obsessive-compulsive disorder (OCD) has long been a unitary diagnosis, there is much recent interest in its potential heterogeneity, as manifested by symptom subgroups. Although the Yale-Brown Obsessive-Compulsive Scale (Y~BOCS) is a widely used instrument to assess obsessive-compulsive symptomat-ology, the variables reflecting the pathogenesis of OCD and Y-BOCS subscores usually were not significantly associateds The aims of this study are to clarify identification of dimensional structure of the symptoms from Y-BOCS checklist and to explore the factor structure of the Y-BOCS. .fethods : Ninety five OCD patients parti-cipated in this study and performed the Y-BOCS and Y-BOCS checklist. The 13 main symptom categories from Y-BOCS checklist and 10 items from Y-BOCS were factor analyzed by using principal components analysis. respectively. Results: Using principal component analysis, we derived 4 factors from 13 main contents of Y-BOCS checklist. Four factors-hoarding/repeating, contamination/cleaning, aggressive/sexual, and religious/som-atic-accounted for more than 60% of the variance. And we derived 3 factors from 10 items of Y -BOCS and these 3 factors-severity of obsession. severity of compulsion, and resistance to symptoms-accounted for more than 70% of variance. Conclusions: The four symptom dimensions from Y-BOCS checklist and three symptom dimensions from Y-BOCS were identified as significant factors accounting for the variance. These factors may be of value in future genetic, neurobiological, and treatment response studies.