The evaluation of defense mechanisms represents one of the most promising fields in the psychodynamic-oriented empirical research on personality disorders (PDs). This study examines the association between DSM-IV PDs and defense mechanisms. We evaluated a sample of 50 adult outpatients seeking personality assessment and psychotherapeutic treatment. PDs have been assessed using the Structured Clinical Interview for DSM-IV Personality Disorder, version 2.0. Defense mechanisms have been evaluated by a group of trained clinical psychologists and psychiatrists (interrater reliability from .61 to .95) using Perry's Defense Mechanism Rating Scale. Our results support the hypothesis that some defense mechanisms underlie PDs and that defenses call for further attention as we assess PDs.