Estimates of HIV/AIDS prevalence are important, because they are the primary measure of the current state of the epidemic in a country. How estimates of HIV/AIDS are made depends on the level of the epidemic. For estimates of HIV/AIDS prevalence in low-level and concentrated epidemics it is necessary to disaggregate the total adult population into sub-groups based on the relative risk of infection. For each group, the major issues and questions are: identifying risk groups, estimating the size of the populations, and estimating HIV prevalence in these groups. The greatest difficulty in making estimates of prevalence in low-level and concentrated epidemics is often establishing the size of various populations. Because of the uncertainty inherent in making an estimate of population size for these groups at high risk, low and high estimates are used. In order to demonstrate the method the case of Honduras was used. The most recent HIV prevalence data and the estimates of population sizes were applied. It was estimated that Honduras, which has a total population of 6,575,000 (United Nations Population Division sources), has approximately 55,000 adults living with HIV/AIDS, with a range of uncertainty between 30,000 and 80,000. Estimations of the burden of HIV is a continuous process and should be updated on a regular basis according to the most recent and relevant information available.