Approximately 10% of HIV-infected patients, the rapid progressors, progress to AIDS within the first 2 to 3 years of HIV infection. Their biological characteristics are not clearly known. They have a particular phenotype (DR) of major histocompatibility complex class-II. Anti-HIV antibodies are not neutralizing and may even be facilitators in vitro. Progressors CTL responses are also defective and the production of the cytokines, specially the chemokines RANTES, MIP-1 alpha et MIP-1 beta which may have a role in inhibition of cellular infection by HIV, is impaired. In addition, the rapid progressors have high levels of inflammatory markers which suppose a chronic activation of the immune system. The virological findings are more inconsistent. A uniform finding is a high viral load that does not fall dramatically after primary HIV infection. Some rapid progressors may be infected with more rapidly replicating, virulent HIV strains. However, the question regarding the homogeneity or the other characteristics of viral load remains to be resolved.