The present measurements of the self-harm are fraught with problems. Their clinical utility is limited and majority of them are better suited for use as a screening or as a research tool. Given the high prevalence rates of the self-harm and the suggestive evidence for its clinical correlates and fatal consequences, this study is important. Additionally, anonymous adolescent-report measures for self-harm are arguably better suited for use compared to other assessment modalities (e.g. structured, semi-structured interviews) in clinical settings. In the light of these, one of the purposes of this book is to systematically review the literature about the nature, epidemiology and the measurements of self-harm. Another purpose is to describe a preliminary assessment of the new instrument: self-harm questionnaire(SHQ). This study is designed as a cross-sectional survey and conducted in Child and Adolescent Mental Health Services in the United Kingdom. The methodological limitations, implications for clinicians and the direction for future research are discussed in the discussion chapter of the book.