BPD is characterized by impulsivity and instability of affect, self-image, and interpersonal relationships. High rates of substance abuse and behaviors that harm self or others have been associated with BPD. Whereas prevalence rates for BPD in the general population are 1-2 percent, rates among both male and female inmates have been estimated at 12-30 percent. Awareness of the behavioral manifestations of BPD and the dysfunctional emotions and cognitions underlying these behaviors can facilitate more effective strategies for managing and treating these individuals during their incarceration. Psychopathy, on the other hand, is related to, but distinct from, the diagnosis of antisocial personality disorder as defined in the Diagnostic and Statistical Manual of Mental Disorders. Psychopathy is characterized by persistent involvement in antisocial behavior, beginning in childhood or adolescence. It includes behavioral symptoms such as impulsivity, deceitfulness, criminal activity, and aggressiveness. Psychopathy is a more severe disorder than antisocial personality disorders. BPD is characterized by many of the behavioral features of psychopathy. In the current study of 479 pretrial and post-trial inmates in a metropolitan area county jail, data were obtained on the prevalence of BPD and psychopathy. Three notable findings were the high rate of BPD among jail inmates, the modest gender difference in BPD among inmates, and the modest correlation between symptoms of BPD and psychopathy. Given the exceptionally high rates of BPD, correctional staff should be trained to have better awareness of this illness and ways to manage and treat it. 4 tables and 52 references