The Brazilian response to the human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) epidemic is being observed all over the world because of its success. Understanding the role of injection drug users (IDUs) in the epidemic and the political response thereto is a key factor in the control of the epidemic in Brazil. This paper summarizes some of the most important analyses of the Brazilian response to the HIV/AIDS epidemic among and from IDUs. Key elements of the response include the support of the Brazilian Universal Public Health System, the provision of universal access to highly active antiretroviral therapy, and the creation of harm reduction projects that are politically and financially supported by the federal government. The response among and from IDUs is a key element in overall control of the HIV/AIDS epidemic. The response to the epidemic among and from IDUs has been headed in the correct direction since its beginning and is now being intensively expanded.