Non-governmental organizations (NGO) can play a critical role in the delivery of HIV prevention services and other assistance to persons living with AIDS. The flexibility of NGOs enables them to respond quickly to fill in gaps in health care and social services. NGOs can do what government agencies cannot do or are not willing to dofor example, reaching out without perceived threat to IDUs and other marginalized sub-groups whose behaviors are often stigmatized and also put them at higher risk of HIV/AIDS. A recent survey of 29 NGOs in Central and Eastern Europe showed that most NGOs targeted injection drug users; provided needle exchange and HIV prevention peer education; and delivered AIDS presentations and distributed educational materials [57] . In Africa, where the main transmission occurs via heterosexual activity, NGOs are most likely to direct their attention to the general public and to youth; they provide peer-education or community outreach [58] . In both Thailand and Brazil, where success has been observed in controlling the HIV/AIDS epidemic or reducing AIDS mortality, NGO are believed to play a key role, but their programs lack rigorous and systemic evaluation [59, 60] . NGOs often face several difficulties: lack of financial resources [57, 58] ; lack of communications with governmental organizations [61] ; governmental indifference or opposition; and AIDSrelated stigma [57] .