Background: The purpose of this study was to assess the temperament and character patterns of obsessive-compulsive disorder (OCD) patients and to investigate the relationship between patterns of temperament and character and the severity of obsessive-compulsive symptoms. Method: The subjects were 40 patients who met DSM-IV criteria for OCD and 40 age-, sex-, and IQ-matched healthy controls. All subjects completed Cloninger's Temperament and Character Inventory. Other instruments included the Yale-Brown Obsessive Compulsive Scale, the Beck Depression Inventory, and the Beck Anxiety Inventory. Results: OCD patients showed significantly higher scores of harm avoidance and lower scorns of novelty seeking and self-directedness compared with healthy comparison subjects. In addition, the high harm avoidance and low self-directedness scores are correlated with a greater severity of obsessive-compulsive symptoms in OCD subjects (multiple regression analysis, β = 0.39, t = 2.54, df = 34, p = .016; β = -0.41, t = 2.46, df = 34, p = .019, respectively). Conclusion: OCD patients had distinct patterns of temperament and character compared with healthy comparison subjects. In addition, these patterns are specifically related to the severity of obsessive-compulsive symptoms.