OBJECTIVE: The purpose of this study was to determine the 10-year course of the psychosocial functioning of patients with borderline personality disorder (BPD). METHOD: The social and vocational functioning of 290 inpatients meeting both the Revised Diagnostic Interview for Borderlines (DIB-R) and DSM-III-R criteria for BPD and 72 axis II comparison subjects were carefully assessed during their index admission. Psychosocial functioning was reassessed using similar methods at five contiguous 2-year time periods. RESULTS: Borderline patients without good psychosocial functioning at baseline reported difficulty attaining it for the first time. Those who had such functioning at baseline reported difficulty retaining and then regaining it. In addition, over 90% of their poor psychosocial functioning was due to poor vocational but not social performance. CONCLUSION: Good psychosocial functioning that involves both social and vocational competence is difficult for borderline patients to achieve and maintain over time. In addition, their vocational functioning is substantially more compromised than their social functioning.