This article explores the hypothesis that self-injurious behavior (SIB) of the type associated with borderline personality disorder (BPD) has an important mood regulatory function. Thirty-eight female inpatients with an Axis II diagnosis of BPD and a history of SIB rated a variety of mood and affective states, using visual analog scales recalled over the course of usual SIB experiences. Subjects were additionally divided into two groups according to whether they typically experience pain during SIB (BPD-P group) or did not (BPD-NP group). For both groups, the visual analog scale ratings revealed significant mood elevation and decreased dissociation following self injury, with a peak in dissociative symptoms during self injury. The ratings of dissociative symptoms were found to be higher in the BPD-NP group when compared to the BPD-P group across all stages of SIB. The ratings of sexual arousal did not change over the course of SIB for either group. These findings are discussed in light of current knowledge of the relationship between SIB and mood.