The purpose of these guidelines is to provide National AIDS Councils (or equivalent) with technical guidance on how to measure the revised list of core indicators for the implementation of the Declaration of Commitment on HIV/AIDS, adopted by Member States of the United Nations during the United Nations General Assembly Special Session on HIV/AIDS in June 2001. These guidelines provide technical guidance on the detailed specifi cations of the core indicators, on the information required and the basis of their construction, and on their interpretation. The guidelines also aim to maximize the validity, internal consistency and comparability across countries and over time of the indicator estimates obtained. In particular, the guidelines aim to ensure consistency in the types of data and methods of calculation employed.