Abstract: Previous studies have shown that IRF11 is a fish-specific gene. There is confusion in nomenclature of IRF1 and IRF11 in the version 9 of the zebrafish genome. Herein, gene synteny of IRF1 and IRF11 was analyzed in some vertebrates, suggesting that IRF11 and IRF1 are two different genes and are not appropriate to name IRF1b and IRF1a, respectively. Phylogenetic tree analysis showed that fish IRF11 shows similar evolution distance to either IRF1 or IRF2, and that fish IRF11 occurred earlier in a vertebrate ancestor than did fish IRF1 and IRF2 likely due to gene loss in nonfish vertebrates during evolution. Like vertebrate IRF1, zebrafish IRF11 resided in nucleus, which was sufficiently directed by a nuclear localization sequence in N-terminal DNA binding domain. Expression analysis revealed that zebrafish IRF11 was transcriptionally induced by poly (I:C), although at a lower level than zebrafish IRF1.