This study examined the relationship between borderline and impulsive personality traits on the one hand, and monoamine function on the other in 15 women with bulimia nervosa and 15 women with recurrent suicidal behavior. Platelet serotonin (5-HT) and platelet monoamine oxidase (MAO) activity were used as peripheral measures of monoaminergic function. All suicide attempters were diagnosed as having a borderline personality disorder, whereas this diagnosis was less frequent in bulimics. Bulimics with borderline comorbidity resembled recurrent suicide attempters with borderline personality disorder more closely in both psychological (anger, impulsive behavior) and biochemical characteristics (platelet 5-HT) than bulimics without borderline personality disorder. Platelet 5-HT was higher in patients with borderline personality than in normal female controls and was positively correlated with the disposition to experience anger. Impulsive personality traits were consistently negatively correlated with platelet MAO activity. Our findings support the subdivision of bulimics according to the presence of borderline or "multi-impulsive" personality disorder.