Document Type


Publication Date



Populations at higher risk for HIV infection are often the most difficult to reach and this is particularly true of men who have sex with men (MSM), injecting drug users, and female sex workers in sub-Saharan Africa. These subpopulations are frequently marginalized by society because of the illicit and/or illegal activities they engage in. Estimating the size of hard-to-reach populations is important to effectively plan, implement, monitor, and evaluate HIV and AIDS prevention and care programs. “Capture-recapture” is a method of estimating the prevalence of a trait in a population or more simply it’s a method that provides a good estimation of the size of a particular population. This method is useful in estimating the sizes of hard-to-reach and stigmatized human populations. The Population Council in collaboration with research partners has conducted and validated capture-recapture enumerations of MSM sex workers in Kenya, South Africa, and Nigeria. This training guide covers topics that include: Why Conduct Research on Most at Risk Populations, What Is Capture-Recapture and How Is It Conducted, and Ethical Considerations for Enumerators.