BACKGROUND AND OBJECTIVES: Mucin is involved in the pathogenesis of otitis media, but little is known about its expression in the mastoid mucosa with chronic otitis media. The purpose of this study is to identify MUC1, 2, 4, 5AC, 5B, 8 gene expression in the mastoid mucosa with chronic otitis media, and to compare the results with normal mastoid mucosa. MATERIALS AND METHOD: Normal or inflamed mastoid mucosal specimen were taken at the time of surgery, who underwent cochlear implant surgery and middle ear surgery for chronic otitis media. The profiles of mucin gene expression were examined by Real time reverse transcription polymerase chain reaction. RESULTS: This study revealed that RT-PCR of cDNAs from mastoid mucosa specimen of chronic otitis media showed the expression of MUC1, MUC4, MUC5AC, MUC5B, and MUC8 but MUC2 was not detected while normal mastoid mucosa showed the same pattern of mucin gene expression. In mastoid mucosa with chronic otitis media, mucin mRNA expression was upregulated in MUC1 1.2+/-1.1, MUC4 3.2+/-2.5, MUC5AC 2.5+/-1.0, MUC5B 4.1+/-2.2, and MUC8 2.7+/-2.1 times compared with that of normal mucosa and MUC5B is statistically significant (p<0.05). The MUC1, 4, 5AC, 5B, 8 mRNA expressions were correlated to infiltration of inflammatory cells in the submucosa of mastoid mucosa with chronic otitis media. CONCLUSION: These results suggest that MUC1, MUC4, MUC5AC, MUC5B, and MUC8 are expressed in the normal and inflamed mastoid mucosa and up-regulated by chronic inflammation.