The UN Commission on Human Rights began establishing the Special Procedures in the late 1960s. Since then, the UN mechanisms have developed and become veritable tools of human rights protection and monitoring.This book endeavours to capture the evolution of the human rights activity carried out by the Special Procedures and evaluate their importance and impact. It provides a thorough and up-to-date insight of the institutional history of the Special Procedures, analyzes their legal dimension, puts forward a conceptual definition of them, elucidates their evolution and assesses their effectiveness.This book makes an important and unique contribution to the study of UN human rights monitoring mechanisms by providing a systematic analysis and conceptualization of the Special Procedures. Also by singling out indicators to evaluate the impact of the Procedures' practice, this study brings innovative elements to the academic debate on the measurement of human rights bodies' activity.