AbstractThis issue of Journal of Clinical Psychology: In Session is devoted to the assessment and treatment of non‐suicidal self‐injury (henceforth self‐injury). In this introductory article, the author describes the scope of behaviors referenced by the term self‐injury, establishes the historical and current relevance of self‐injury for clinical practice, and summarizes the articles that appear in this issue. Self‐injury is the intentional destruction of body tissue without suicidal intent and for purposes not socially sanctioned. This issue addresses many aspects of self‐injury, including its prevalence, functions, assessment, and treatment. The articles feature case illustrations and treatment recommendations, and all have direct implications for clinical practice. © 2007 Wiley Periodicals, Inc. J Clin Psychol: In Session 63: 1039–1043, 2007.