This study has two purposes. The first purpose is to describe the severity of sexual abuse reported by a well-defined sample of borderline inpatients. The second purpose is to determine the relationship between the severity of reported childhood sexual abuse, other forms of childhood abuse, and childhood neglect and the severity of borderline symptoms and psychosocial impairment. Two semistructured interviews of demonstrated reliability were used to assess the severity of adverse childhood experiences reported by 290 borderline inpatients. It was found that more than 50% of sexually abused borderline patients reported being abused both in childhood and in adolescence, on at least a weekly basis, for a minimum of 1 year, by a parent or other person well known to the patient, and by two or more perpetrators. More than 50% also reported that their abuse involved at least one form of penetration and the use of force or violence. Using multiple regression modeling and controlling for age, gender, and race, it was found that the severity of reported childhood sexual abuse was significantly related to the severity of symptoms in all four core sectors of borderline psychopathology (affect, cognition, impulsivity, and disturbed interpersonal relationships), the overall severity of borderline personality disorder, and the overall severity of psychosocial impairment. It was also found that the severity of childhood neglect was significantly related to five of the 10 factors studied, including the overall severity of borderline personality disorder, and that the severity of other forms of childhood abuse was significantly related to two of these factors, including the severity of psychosocial impairment. Taken together, the results of this study suggest that the majority of sexually abused borderline inpatients may have been severely abused. They also suggest that the severity of childhood sexual abuse, other forms of childhood abuse, and childhood neglect may all play a role in the symptomatic severity and psychosocial impairment characteristic of borderline personality disorder.