The aims of this study were to examine differences in clinical features, impairment, and types of childhood traumas among women with borderline personality disorder (BPD), women with BPD and posttraumatic stress disorder (PTSD), and those with other personality disorders and PTSD. Using baseline data from the Collaborative Longitudinal Study of Personality Disorders, 186 women were divided into 3 groups (BPD+PTSD, BPD, PTSD), based on structured diagnostic interviews for Axis I and Axis II disorders and compared on selected clinical variables. The additional diagnosis of PTSD in borderline women did not significantly increase the degree of borderline pathology and psychiatric morbidity but did significantly increase general dysfunction and the occurrence of hospitalization. The additional diagnosis of BPD in women with PTSD significantly increased the features of suicide proneness and impulsiveness. Both groups of women with PTSD reported significantly more types of childhood traumas relative to borderline women without PTSD. Consistent with other research, the findings suggest that PTSD does not appear to alter the central features of BPD. The clinical implications of our findings are considered.