Background and Objectives：It is believed that the innate imunity plays a critical role in protecting the tubotympanum from l molecules, defensins have been shown to contribute significantly to innate imunity. However, it is still unclear whether or not β defensins are expressed in human middle ear mucosa. Materials and Method：Imunolabeling and RT-PCR were performed with the mucosal specimen from normal subjects and otitis media patients, respectively. Expression of β defensin 2 mRNA was compared between the control group and experimental group that was treated by inflammatory stimuli in the animal models using RT-PCR. Results：β defensin 1 was expresed in both normal and inflamed middle ear mucosa of human, but β defensin 2 and 3 were found only in the inflamed mucosa. The expresion of β defensin 2 mRNA was up-regulated when the interleukin-1α (IL-1α) or lipopolysaccharide (LPS) was treated in the middle ear mucosa of the experimental animals. Conclusion：We could show that β defensins are expressed in the human middle ear mucosa and that βmatory stimuli, IL-1α or LPS.