The course of the HIV infection has been dramatically modified since the introduction of highly active antiretroviral therapy (HAART) combining inhibitors of the HIV-1 reverse transcriptase and protease. Despite some controversies about the extent to which the immune system can normalize, it is generally admitted nowadays that a numerical and functional CD4 cell profile more akin to asymptomatic HIV-infected individuals can be restored in AIDS patients and can confer host protection against opportunistic events. The best hallmark of such immune restoration is the massive decline in the mortality and morbidity related to AIDS that have been registered in all industrialized countries. These changes involve a recirculation of mature peripheral T cells, a regeneration of naive T cells from thymic origin and a restoration of memory CD4 T cell réactivities. Although these recent advances warrant increased optimism, HAART by reducing the virus burden is unable to restore immunity against HIV itself, except when introduced at the very early stage after virus inoculation. The single condition required for immune reconstitution is an efficient and durable inhibition of virus replication. These positive effects can be obtained at late stages of the disease even when the patients have been heavily pre-treated. They also demonstrate that HIV does not definitively alter the lymphoid tissues nor the immune defenses, even aller years of infection and severe immune suppression, except for HIV-specific CD4 T helper cells.