Accurate information is a vital requirement to enable the most effective international response to AIDS. These guidelines provide National AIDS Councils (or equivalents) with technical guidance on how to measure the core indicators for the implementation of the Declaration of Commitment on HIV/AIDS, adopted by Member States of the United Nations during the General Assembly Special session on HIV/AIDS in June 2001. Included are the detailed specifications of the core indicators, the information required and the basis of their construction, and their interpretation.