Earlier studies have demonstrated emotional overreactions to affective visual stimuli in patients with borderline personality disorder (BPD). However, contradictory findings regarding hyper- versus hyporeactivity have been reported for peripheral physiological measures. In order to extend previous results, the authors investigated emotional reactivity and long-term habituation in the acoustic modality. Twenty-two female BPD patients and 19 female nonclinical controls listened to emotionally negative, neutral, and positive sounds in two identical sessions. Heart rate, skin conductance, zygomaticus/corrugator muscle, and self-reported valence/arousal responses were measured. BPD patients showed weaker skin conductance responses to negative sounds than controls. The elevated zygomaticus activity in response to positive sounds observed in controls was absent in BPD patients, and BPD patients assigned lower valence ratings to positive sounds than controls. In Session 2, patients recognized fewer positive sounds than controls. Across both groups, physiological measures habituated between sessions. These findings add to growing evidence toward partial affective hyporeactivity in BPD.