A common denominator of all the major infections found concurrently with HIV is immune activation. Though the type and characteristics of this activation differ among the various infections, the result is invariably increased HIV infection and replication. Furthermore, the immune activation may affect other concurrent infections such as tuberculosis. Therefore, eradication or suppression of concurrent infections in HIV-infected people may have a major impact on the spread and progression of HIV infection and AIDS, and also on protective HIV vaccines. This applies particularly to developing countries, where these infections are common and no antiretroviral therapy is available. Further studies are urgently needed to clarify and further characterise the long-term effects of concurrent infections on the spread and progression of HIV/AIDS, and particularly on the immune response of the infected host.