This study examined the impact of comorbid personality disorders on the outcome of cognitive behavioral treatment for women with chronic posttraumatic stress disorder (PTSD). Seventy-five adult women with PTSD resulting from rape or nonsexual assault in adulthood or sexual abuse in childhood were treated with prolonged exposure with or without cognitive restructuring. Assessment of personality disorders found that 39% of participants met DSM-IV criteria for some personality disorder diagnosis. No difference was found between women with and without personality disorders on the prevalence of PTSD at the end of treatment. Participants with a personality disorder were less likely to attain good end-state functioning, but this may be attributable to the fact that they started off slightly worse than those without personality disorders. Finally, the comorbid patients treated by community therapists fared as well or better than those treated by cognitive behavioral treatment experts in posttreatment prevalence of PTSD and end-state functioning.