The purpose of the study was to examine the role of several psychological risk factors-childhood sexual abuse (CSA) and its parameters, childhood physical abuse and its parameters, early separation or loss, and abnormal parental bonding-in male patients with borderline personality disorder (BPD). Subjects with personality disorders were divided into BPD (N = 61) and non-BPD (N = 60) groups. The risk factors were measured by a developmental interview and the Parental Bonding Index. The BPD group had a higher frequency of CSA, more severe CSA, a longer duration of physical abuse, increased rates of early separation or loss, and a higher paternal control score on the Parental Bonding Index. CSA and separation or loss were significant in the multivariate analysis. The risk factors suggest that trauma and loss, as well as problems with fathers, are important for the development of BPD in males.