In this paper we encourage the evaluating clinician to approach substance abuse as though it were a symptom, like any other, that serves a psychological function for the borderline individual. During the assessment phase, this approach is likely to (1) generate interest among treaters (2) solidify rapport with the patient resulting in a positive attitude toward the assessing clinician with more informative self-reports, (3) elucidate, for the clinician, the patient's major deficits in personality structure, especially the inability to understand and control affective states, and (4) stimulate the patient's curiosity about the way in which emotions are perceived and processed.