The diagnosis of HIV infection is generally lead using two different ELISAs to detect specific anti-HIV antibodies, the eventual reactivity must then be confirmed by a Western Blot The antibodies can be detected only 1-6 months after the infection; in fact in the earliest phases neither the antibodies, for their low titre, nor the specific antigens, for the antibodies could form immune complexes, can be detected by the achieved methods. Only the viral isolation can reveal the presence of the virus in this early phase, but the isolation must be conducted only in adequately safe laboratories (P3 laboratories). The only test able to replace the viral isolation is the Polymerase Chain Reaction (PCR). The PCR technique can be useful to reveal an HIV infection in its early phase and to monitor the infection progression and the efficacy of an antiretroviral treatment