It has been suggested that people engage in nonsuicidal self-injury (NSSI) because they (a) experience heightened physiological arousal following stressful events and use NSSI to regulate experienced distress and (b) have deficits in their social problem-solving skills that interfere with the performance of more adaptive social responses. However, objective physiological and behavioral data supporting this model are lacking. The authors compared adolescent self-injurers (n = 62) with noninjurers (n = 30) and found that self-injurers showed higher physiological reactivity (skin conductance) during a distressing task, a poorer ability to tolerate this distress, and deficits in several social problem-solving abilities. These findings highlight the importance of attending to increased arousal, distress tolerance, and problem-solving skills in the assessment and treatment of NSSI.