All members of Group VI use virally encoded reverse transcriptase, an RNA-dependent DNA polymerase, to produce DNA from the initial virion RNA genome. This DNA is often integrated into the host genome, as in the case of retroviruses and pseudoviruses, where it is replicated and transcribed by the host.
Group VI includes:
* Order Ortervirales
** Family Belpaoviridae
** Family Metaviridae
** Family Pseudoviridae
** Family Retroviridae – Retroviruses, e.g. HIV
** Family Caulimoviridae – a VII group virus family (see below)
The family Retroviridae was previously divided into three subfamilies (Oncovirinae, Lentivirinae, and Spumavirinae), but are now divided into two: Orthoretrovirinae and Spumaretrovirinae. The term oncovirus is now commonly used to describe a cancer-causing virus. This family now includes the following genera:
* Subfamily Orthoretrovirinae:
** Genus Alpharetrovirus; including Avian leukosis virus and Rous sarcoma virus
** Genus Betaretrovirus; including Mouse mammary tumour virus
** Genus Gammaretrovirus; including Murine leukemia virus and Feline leukemia virus
** Genus Deltaretrovirus; including Bovine leukemia virus and the cancer-causing Human T-lymphotropic virus
** Genus Epsilonretrovirus
** Genus Lentivirus; including Human immunodeficiency virus 1 and Simian and Feline immunodeficiency viruses
* Subfamily Spumaretrovirinae:
** Genus Bovispumavirus
** Genus Equispumavirus
** Genus Felispumavirus
** Genus Prosimiispumavirus
** Genus Simiispumavirus
Note that according to ICTV 2017, genus Spumavirus has been divided into five genera, and its former type species Simian foamy virus is now upgraded to genus Simiispumavirus with not less than 14 species, including new type species Eastern chimpanzee simian foamy virus.