We have investigated the biological effects of recombinant IL-1$eta$ (rIL-1$eta$) on the expression of antiviral genes such as Myxovirus-3 (MX-3) and Interferon regulating factor-1 (IRF-1), which are related to type I interferon. When ten micrograms of rIL-1$eta$ were treated, we observed the stimulatory effect on the expression of these antiviral genes. Interestingly, at the early stage of stimulation, these genes were down-regulated and then up-regulated by the results obtained that the expressions of these genes were decreased at day 1 post-injection and gradually increased at day 3 post-injection. Thus, the stimulatory effect of rIL-1$eta$ on the expression of MX-3 and IRF-3 gene might be an indirect stimulatory effect because significant up-regulation was delayed until day 3 post-injection