Self-injurious behaviors, including nonsuicidal self-injury (NSSI) and suicidal behaviors, are remarkably prevalent and woefully understudied. This area of research involves numerous methodological, ethical, and practical challenges that have limited progress in understanding some of the most basic characteristics and correlates of self-injurious behavior. To date, relatively little data are available to develop empirically based preventions or interventions, and no empirically supported treatments currently are available to reduce NSSI or suicidality in most populations. The articles in this special section offer examples of methodologically innovative, theoretically based work that address these research needs. Articles in this special section include studies of functional models of NSSI, studies that examine more distal risk factors for NSSI, and studies of suicidality. A brief review of current research in these areas is offered.