This article reviews the nature and prevalence of nonsuicidal self-injury (NSSI) and suggests how it can be better recognized and treated in the mental health community. Throughout history, NSSI has been a core element of many types of rituals (e.g. cultural, religious, spiritual, and healing rituals) and is now also regarded as a pathological expression of emotional pain, particularly in Western cultures, where its occurrence has increased dramatically since the 1980s. NSSI involves the direct and deliberate self-infliction of bodily harm without suicidal intent. Self-injury can be viewed as a distinct mental health disorder, a defining criterion of other mental disorders, or a transient response to trauma or stress. Notwithstanding its etiology, NSSI should become a more salient aspect of psychiatric evaluation and intervention considering its frequency of occurrence and deleterious consequences, especially among young people. The current article consists of six sections that describe the terminology associated with NSSI; its general prevalence, measurement, and variability (age, race, and gender); its relationship with other psychiatric illness; and its diagnosis and treatment.