This document defines and provides background information on indicators to monitor progress toward the United Nations Millennium Development Goals. It was produced through interagency collaboration led by the United Nations Population Fund and involving the UN Development Programme, UN Statistics Division, World Bank, and others. The document introduces 48 quantitative indicators grouped under the 8 Millennium Goals covering issues such as poverty, education, gender equality, health, environment and global partnership. For each indicator, definitions are provided as well as the rationale, concepts, and data sources to help monitor progress toward achieving the Goals.