We assessed the potential relationship between personality disorder (PD) clusters, as assessed by the SCID-II, and temperamental traits assessed by the Tridimensional Personality Questionnaire (TPQ) among a well-characterized, unmedicated cohort of outpatients with major depressive disorder (MDD). The TPQ and SCID-II were administered to 263 depressed outpatients (mean age = 39.9 +/- 10.5 years; women = 139, 53%; initial 17-item Hamilton Rating Scale for Depression = 19.6 +/- 3.4) who currently met criteria for MDD and who were enrolled in an 8-week treatment trial. The multiple linear regression method was used to evaluate the relationship between TPQ factors and personality disorder clusters, controlling for age, gender, and initial 17-item Hamilton Rating Scale for Depression score as necessary. Among outpatients with MDD, meeting criteria for a Cluster A PD diagnosis was related to high harm avoidance (HA) scores, as well as low reward dependence and novelty seeking (NS) scores. Additionally, high HA scores were associated with meeting criteria for a Cluster C PD diagnosis, while high NS scores were associated with meeting criteria for a Cluster B PD diagnosis. Certain temperament traits, especially HA and NS, appear to be associated with specific patterns of personality clusters among depressed patients.