Sudden sensorineural hearing loss (SSNHL) and Ménière’s disease are the most common inner ear diseases in which the causes are unknown. As recent magnetic resonance imaging has demonstrated disruption of the blood–labyrinth barrier in these inner ear diseases, inflammatory reaction associated with increased permeability of the blood vessels may be involved. The genotypes of interleukin 1A (IL1A) (−889C/T; rs1800587) and interleukin 1B (IL1B) (−511C/T; rs16944) were determined using an allele-specific primer–polymerase chain reaction method in 72 patients with SSNHL, 68 patients with Ménière’s disease, and 2202 control subjects living almost in the same area as the patients. A significantly higher prevalence of the IL1A−889T allele was observed in SSNHL and Ménière’s disease compared with controls, although no significant difference in distribution of IL1B−511C/T genotypes was observed between the patients and controls. Adjusted odd ratios for SSNHL and Ménière’s disease risks in the −889TT genotypes were 25.89 (95% confidence interval (CI) 12.19–54.98) and 18.20 (95% CI 7.80–42.46), respectively, after age and gender were taken as moderator variables. Our results suggested that IL1A is closely associated with susceptibility of SSNHL and Ménière’s disease.