OBJECTIVE : Unfolded proteins in the endoplasmic reticulum (ER) cause an ER stress response and can result in various pathologic conditions, including inflammation. Otitis media is the most common disease in otolaryngology and is associated with inflammation. The pathophysiology of chronic otitis media is not well understood; we therefore investigated the expression pattern of ER stress-related mRNAs in chronic otitis media. METHODS : Specimens were obtained from 47 patients with chronic otitis media over a period of 2 years. Expression levels of 6 ER stress transcription factors were quantitatively assessed using real-time RT-PCR. RESULTS : The mRNA expression of sXBP1 was significantly higher in the otorrhea present group than in the otorrhea absent group (p < 0.05). ATF6 expression was significantly higher in the ossicle destruction group than in the ossicle intact group (p < 0.05). mRNA expression of the 6 ER stress-related genes did not differ significantly between those patients with positive microbial cultures versus those with negative cultures (p > 0.05) or those with facial nerve dehiscence versus those without facial nerve dehiscence (p > 0.05). CONCLUSIONS : sXBP1 appears to be involved in chronic otitis media-associated inflammation, including otorrhea. ATF6 is associated with the destruction of ossicles. Our results suggest that certain ER stress-related genes are expressed in chronic otitis media-associated inflammation.