Participants included 44 men and 38 women. They completed the Structured Clinical Interview for DSM-III-R, parts I and II, and discussed their histories of victimization by physical and sexual assault. Results revealed that 60 percent met criteria for a personality disorder. The 43 persons who had experienced assault were significantly more likely to have all types of personality disorder diagnoses. Compared with those reporting adult assault only, those who reported childhood assault were more likely to have Cluster B personality disorders and to meet criteria for more than two personality disorder diagnoses. Personality disorders were commonly diagnosed in this group of treatment-seeking, drug-dependent individuals. Findings indicated that the effect of drug abuse as well as assault on the development and presentation of personality disorders is likely to be substantial. Tables and 23 references (Author abstract modified)