In order to further understand the evolutionary scenario of IFITM family, we investigated the chromosomal distribution of well-defined IFITM genes including IFITM1, IFITM2, IFITM3, IFITM5, IFITM6, and IFITM10. Because IFITM7 has chromosome location independent from any other IFITM genes, and only mouse and rat have IFITM7 gene, we did not take it into account in this analysis. Orthologous relationships between IFITM family members were well confirmed with conserved syntenies (Fig. 4A ). All these genes are located in one chromosome and form two loci in terrestrial vertebrates, except in cow that has two loci in two different chromosomes. With the exception of IFITM10, that is located at one locus, all other IFITM genes gather together and form a gene-cluster in the other locus. In teleosts (e.g. zebrafish), the two loci are dispersed in two different chromosomes. Although we identified two loci in two scaffolds of frog, whether they are dispersed in two different chromosomes is still unknown. We investigated genes flanking both sides of the two IFITM loci, and found that the two loci have almost completely same flanking genes from lower (e.g. zebrafish) to higher (e.g. human) vertebrate species. These findings suggest that chromosomal fusion might have occurred during the vertebrate evolution from aquatic to terrestrial species. Furthermore, all these IFITM genes have two exons, and the IFITM gene-clusters exhibit consistent gene order in four hominids, two rodents and three birds, supporting the syntenic relationship of IFITM genes.