Two cohorts of patients with a phenotype of HIV resistance exist in France. The ANRS CO15 ALT cohort was set up in 1994. 71 patients were enrolled defined on immunological criteria: CD4 T cell count above 600/mm3 with a stable or increasing count (positive or zero slopes) on at least three consecutive exams performed during the last 5 years whatever the viral load was, with a known HIV infection for at least 8 years. A consortium of research teams has studied the immunovirological characteristics of these patients. After 16 years of follow-up, 6 patients are still actively followed. The main results have shown the lack of deletion in viral genes nor any functional viral defects, a small size for the viral reservoir, and distinctive genetic characteristics of the host (HLA, chemokines) which lead to potent immune cell responses associated with virus control.