The percentage of adult females living with HIV who are receiving antiretroviral therapy. Limitations and exceptions: The limited availability of data on health status is a major constraint in assessing the health situation in developing countries. Surveillance data are lacking for many major public health concerns. Estimates of prevalence and incidence are available for some diseases but are often unreliable and incomplete. National health authorities differ widely in capacity and willingness to collect or report information. Statistical concept and methodology: Data on HIV are from the Joint United Nations Programme on HIV/AIDS (UNAIDS). Changes in procedures and assumptions for estimating the data and better coordination with countries have resulted in improved estimates of HIV and AIDS. For example, improved software was used to model the course of HIV epidemics and their impacts, making full use of information on HIV prevalence trends from surveillance data as well as survey data. The software explicitly includes the effect of antiretroviral therapy when calculating HIV incidence and models reduced infectivity among people receiving antiretroviral therapy, which is having a larger impact on HIV prevalence and allowing HIV-positive people to live longer. The software also allows for changes in urbanization over time - important because prevalence is higher in urban areas and because many countries have seen rapid urbanization over the past two decades. Antiretroviral therapy has led to huge reductions in death and suffering of people with advanced HIV infection. Standard antiretroviral therapy consists of the use of at least three antiretroviral drugs to maximally suppress HIV and stop the progression of HIV disease. Data are collected through three international monitoring and reporting processes: country responses to the WHO; research by the Interagency Task Team on Prevention of HIV Infection in Women, Mothers and their Children; and country report to UNAIDS through the United Nations General Assembly Special Session Declaration of Commitment on HIV/AIDS.