The aim was to characterize the role of sympathetic nervous system (SNS) functioning in interpersonal dysfunction in those with Borderline Personality Disorder (BPD). It was hypothesized that patients with BPD would experience greater SNS activation during interpersonal interactions. 110 romantic couples (one partner was selected for psychopathology) discussed the greatest disagreement in their relationship for 10 minutes while skin conductance data and behavioral states were coded. Results indicate that BPD patients experienced decreased SNS activation.