The nucleoprotein (N), phosphoprotein (P) and glycoprotein (G) genes of Irkut and West Caucasian bat viruses (WCBV) were sequenced and compared with those of other lyssaviruses. N gene nucleotide identities provided unequivocal separation of all lyssavirus genotypes with an identity threshold of 82%. On this basis, Irkut virus should be considered as a new genotype with particular relatedness to genotypes 4 and 5 (78.0-78.6% identity for N gene nucleotides and 90.4-92.6% for amino acids). Furthermore, genotypes 4-6, together with Aravan, Khujand and Irkut viruses, present a solid phylogroup of Old World bat lyssaviruses. This relationship is apparent using all three viral genes, and causes overlap between intragenotype and intergenotype identities for the P gene (Aravan, Khujand viruses and genotype 6) and for the G gene (Aravan, Khujand, genotypes 5 and 6). WCBV is the most divergent of known lyssaviruses with only limited relatedness to genotypes 2 and 3.