Clinical theories of borderline personality disorder (BPD) identify attachment insecurity as the basis of its characteristic disturbed interpersonal functioning. The purpose of this study was to compare attachment ratings in rigorously diagnosed BPD, depressed (MDD), and nonborderline comparison groups and their correlations to features of interpersonal disturbance. Subjects self-reported ratings on attachment styles using the relationship questionnaire. BPD subjects reported higher scores on both preoccupied and fearful attachment styles than both MDD and nonborderline comparison groups. A mixed model of preoccupied and fearful attachment was more prevalent in the BPD group and was associated with 3 to 20 times greater risk for diagnosis of BPD. Scores on preoccupied and fearful attachment styles were correlated with features of interpersonal disturbance in BPD. A combination of preoccupied and fearful self-reported attachment styles is more specific to BPD than either style alone or attachment insecurity in general.