Aquaporins (AQPs) are integral membrane proteins engaged in the modulation of water homeostasis, but the roles they play in chronic otitis media (COM) have not been well investigated. Accordingly, we undertook document relations between the mRNA expressions of AQPs and COM, and explored the relation between these expressions and otorrhea, which is one of the most common symptoms of COM.Levels of the mRNAs of AQP 1, 2, 3, 4, 5, 6, 8, and 10 were assayed by real-time polymerase chain reaction in inflammatory tissue samples from 81 patients with COM with or without otorrhea. Relationships between AQP mRNA levels and the presence or absence of otorrhea, the presence or absence of bacteria, hearing threshold levels, types of hearing loss, and clinical manifestations were also evaluated.AQP 1, 2, 3, 4, 5, 6, 8, and 10 mRNAs were expressed in inflammatory tissues obtained from all 81 patients with COM with or without otorrhea. AQP 5 mRNA was most expressed in, followed in descending order by AQP 3, 1, 10, 6, 8, 2, and 4. There were no significant intergroup differences in terms of age, sex, duration of illness, levels of hearing loss in both ears, or incidences of conductive or sensorineural hearing loss. However, AQP 4 (P=0.035) and 6 (P=0.085) mRNA levels were significantly lower in the otorrhea group. In addition, bacteria culture positivity (P=0.014) and the incidence of sensorineural hearing loss (P=0.020) were higher in the otorrhea group.AQP 1, 2, 3, 4, 5, 6, 8, and 10 are involved in the development of COM. Specifically, it shows reductions in AQP 4 and 6 mRNA levels, as observed in the otorrhea group, have an effect on the clinical manifestations of COM.