Individuals with borderline personality disorder are diagnostically and clinically characterized by self-harm behavior, as indicated by the criterion in the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision, “recurrent suicidal behavior, gestures, or threats, or self-mutilating behavior.” However, individuals with borderline personality disorder can display externalized aggressive behavior, as well. In an area characterized by considerably less research, empirical evidence indicates that individuals with borderline personality disorder may exhibit physical violence toward partners, physical violence toward known but nonintimate individuals, criminal behaviors that embody externalized violence (e.g., property damage), and, on very rare occasion, murderous behavior (either of family members or anonymous others through serial killing). Given this under-researched area, there are probably other types of externalized aggressive behaviors that have not been empirically revealed. However, externalized aggressive behaviors in individuals with borderline personality disorder clearly exist and need to be assessed in both psychiatric and primary care settings in an effort to promote safety of medical personnel and effective patient management.