Borderline personality disorder (BPD) is a common disorder associated with emotional dysregulation and other symptoms that have been hypothesized to be related to dysfunction of limbic brain areas including hippocampus and amygdala. The purpose of this study was to measure hippocampal and amygdala volumes in BPD. Hippocampal and amygdala volumes were measured with magnetic resonance imaging (MRI) in 10 patients with BPD and 23 control subjects. Patients with BPD had a 21.9% smaller mean amygdala volume and a 13.1% smaller hippocampal volume, compared to controls. These findings are consistent with the hypothesis that alterations in the hippocampus and amygdala are associated with BPD.