The precise interrelationship between borderline personality disorder (BPD) and major depression (MD) remains unclear. To elucidate this further, we studied the characteristics of BPD in an unselected sample of 103 depressed subjects. All subjects were evaluated with structured diagnostic instruments. We contrasted three groups (MD plus BPD, MD plus a non-BPD, and MD plus no personality disorder) across several domains (characteristics of the depressive disorder, psychometric scales, axes I and II comorbidity, early environmental indices, family psychiatric history, and treatment response). Depressed subjects with BPD had significantly earlier onset of depression, dense axes I and II comorbidity, and higher prevalence of conduct disorder, and were characterized by elevated psychoticism and anger-hostility scores. In most other respects, however, depressed subjects with BPD were not strikingly distinct from other groups of depressed subjects.