The recent isolation of GB viruses A and B from GB agent infected tama
rins and their lack of involvement in human hepatitis has sparked inte
rest in the origin of these viruses. Several healthy non-human primate
species have been shown to harbour sequences 52-79% identical to the
GBV-A 5' nontranslated region. In this paper we report the near genome
length sequence of GBV-A(mx), 70047 and GBV-A(tri) 1122. These sequen
ces support previous observations about the genomic organization of GB
V-A and provide insight into the genomic variability within this virus
genus. Although the GBV-A variant polyproteins possess many motifs co
nserved between other members of the Flaviviridae, they do not encode
a basic core-like protein. Amino acid sequence comparisons and phyloge
netic analysis demonstrate variability within the GBV-A genus similar
to that observed between hepatitis C virus (HCV) types. However, genom
ic organization and disease association demonstrate a closer evolution
ary relationship to GBV-C than to HCV.