This statement by some members of a subcommittee empowered by the International Committee on the Taxonomy of Viruses proposes that the acquired immunodeficiency syndrome (AIDS) retroviruses be officially designated as the human immunodeficiency viruses (HIV). Adoption of an internationally acceptable name for this group of viruses has become important in view of the multiplicity of names currently in use. Several isolates of what are evidently closely related members of the same virus group have been called lymphadenopathy-associated virus (LAV) human T-lymphotropic virus type III (HTLV-III) HTLV-III/LAV and several other designations. The name HIV conforms to common nomenclature for retroviruses in that it begins with the host species ends with virus and contains a word that denotes the major pathogenic property of members of the virus group. It is readily distinguishable from all existing names for this group of viruses and was chosen without regard to priority of discovery. The name is sufficiently distinct from the names of other retroviruses to imply an independent virus species. Retroviruses isolated from subhuman primates and found to be genetically related and biologically similar to HIVs should be designated as immunodeficiency viruses of the host species eg simian immunodeficiency virus (SIV). Since HIV isolates are numerous and display considerable genetic heterogeneity particularly in the env gene each laboratory will have to assign subspecies designations to their isolates. It is recommended that each laboratory adopt a code with geographically informative letters and sequential numbers to identify their isolates. Initially existing well characterized isolates such as HTLV-IIIB should be so identified in publications to ease the transition to a unified nomenclature.