The reasons for the failure of the immune system to control HIV-1 infection, and the resulting immunodeficiency, remain unclear. HIV-1 persists in its host despite vigorous immune responses, including a strong, and probably functional, HIV-specific cytotoxic T-lymphocyte response. Interestingly the immunological features of HIV-1-infected individuals show many similarities to those seen in elderly people without HIV infection. We propose that, through a process of continuous immune activation, HIV-1 infection leads to an acceleration of the adaptive immune system ageing process, resulting in premature exhaustion of immune resources, which participates in the onset of immunodeficiency. This hypothesis might shed new light on HIV-1 pathogenesis and could suggest the need to reconsider current immunotherapeutic strategies to fight the virus.