Mouse guanylate-binding protein 3 (mGBP3) is a 71-kDa GTPase which belongs to GTP-binding protein family. The present study showed that the expression of mGBP3 transcript was readily induced in a dose dependent fashion in the macrophage cell line RAW264.7 treated with either $interferon-{gamma} (IFN-gamma)$ or lipopolysaccaride (LPS). The expression of mGBP3 protein was also apparent by 4 and 6 h after the treatment of cells with IFN-gamma (100 U/ml) or LPS ($1{mu}g/ml$) , and remained at palteau for at least 24 h. Cycloheximide ($10{mu}g/ml$) had no effect on the $IFN-gamma-$ or LPS-induced mGBP3 expression, suggesting that the mGBP3 induction did not require further protein synthesis. Interestingly, a protein kinase C (PKC) inhibitor staurosporine (50 nM) abolished the induction of mGBP3 expression by LPS, but not by $IFN-{gamma}$. These findings suggest that mGBP3 may be involved in the macrophage activation process and both IFN-gamma and LS induce the mGBP3 expression through distinct signal transduction pathways.