This article critically reviewed the research addressing the epidemiology and phenomenology of non-suicidal self-injury (NSSI) among adolescents. Articles were identified through a search of Medline and Psychinfo. Findings indicate a lifetime prevalence of NSSI ranging from 13.0% to 23.2%. Reasons for engaging in NSSI include to regulate emotion and to elicit attention. Correlates of NSSI include a history of sexual abuse, depression, anxiety, alexithymia, hostility, smoking, dissociation, suicidal ideation, and suicidal behaviors. Suggested areas of future research include identifying the psychiatric diagnoses associated with NSSI among adolescents, determining the temporal link between NSSI and suicide attempts, learning more about the course of NSSI, understanding the biological underpinnings of NSSI, and identifying effective treatments for NSSI in adolescents.