Personality disorders are life-long maladaptive behavioral patterns. Borderline personality disorder (BPD) is the leading personality disorder encountered in clinical settings, often associated with tremendous distress. It is characterized by impulsivity, emotional lability, unstable interpersonal relationships, with particular sensitivity to abandonment. BPD patients are prone to self destructive behaviors and all too frequently attempt suicide. When in emotional turmoil, persons with BPD may also develop brief, transient psychotic states. Psychotherapy for BPD is a common treatment option, but it requires considerable time and specific personnel training, and is therefore not always feasible. Medical treatment is an efficacious alternative, however there is no concensus on drug selection. Some experts have suggested that medical treatment should be selected individually according to the subject's dominant clinical symptom. Several psychopharmacological groups have been proposed: Antidepressants, mood stabilizers, and several novel antipsychotic drugs. The latter are particularly promising since they may produce symptomaic improvement with fewer adverse effects. Risperidone has been shown in a few preliminary studies to be promising in the treatment of various BPD symptoms, but no controlled study has tested it yet. We propose to test the efficacy of risperidone in the treatment of BPD in a double-blind crossover design using both clinical and phsysiological measure.The main hypothesis is that risperidone will be efficient in alleviating BPD core and secondary symptoms.