14 self-mutilators & 14 psychiatric controls were administered the Diagnostic Interview for Borderlines. Consistent with Gunderson’s theory of borderline personality disorder, the self-mutilators scored significantly higher on impulse-action patterns, affects, psychoticism, & interpersonal relations as well as on the total borderline index. The results have implications for developmental theory, diagnosis & treatment & provide support for validity & utility of the Diagnostic Interview.