Artemisia princeps Pampanini (AP) was fermented with Bifidobacterium infantis K-525 and its antiasthmic effect investigated. AP and fennented AP (FAP) reduced the IgE level in the blood of ovalbumin-induced asthmic mice. Moreover, FAP reduced the IgE, proinflammatory cytokine IL-6, and IL-4 levels in the trachea, as well as in the lung of the experimental asthmic mice, whereas AP only reduced the IgE and IL-6 levels in the lungs. Nonetheless, AP and FAP both inhibited the mRNA expression of IL-6 and TNF-${alpha}$ in IgE-induced RBL-2H3 cells. The in vivo antiasthmic effect of FAP was more potent than that of AP. Therefore, these findings suggest that the enhanced antiasthmic effect of AP after bifidus fermentation was possibly due to the regulation of the proinflammatory cytokine biosynthesis of IL-6 and TNF-${alpha}$.