Objective: This study evaluates the therapeutic effect of fluoxetine, a selective serotonin reuptake inhibitor, in borderline personality disorder. Method: 46 patients with borderline personality disorder according to DSM-III-R and Diagnostic Inteview for Borderlines (DIB-R) criteria, were given fluoxetine 20-60 mg for seven weeks. They were evaluated each week using Brief Psychiatric Rating Scale (BPRS), Global Assessment of Funtioning Scale (GAF), Hamilton Depression Rating Scale (HDRS) and a clinical Impulsivity Scale. Results: there were significant improvements in BPRS, HDRS, GAF and Impulsivity Scale from the first week of the treatment. These improvements continued until the seven week of treatment. The favourable outcome was not only due to the improvement in depression and impulsivity scores, but also to the decline of global psychopathology. Conclusions: the data suggest that fluoxetine is an effective pharmacologic treatment for borderline personality disorder. These finding