This study analyzes a method of indirect marking of T lymphocytes subpopulations using a 2nd antibody coupled to colloidal gold particles (Immunogold). There is an excellent correlation between this technique and the classical technique of indirect immunofluorescence. Immunogold enables an easy and rapid count of lymphocytes CD4+ and CD8+ during infections secondary to HIV virus (LAV/HTLV III). The permanent nature of the preparations and the cytological control make this method an interesting tool for the diagnosis and follow-up of patients suffering from AIDS, ARC or only asymptomatic seropositive individuals.