Objective:To analyze the clinical characteristics and treatment effect between bilateral(bi-)and unilateral(uni-) sudden sensorineural hearing loss(SSNHL).Method:Four hundred and eighty cases of SSNHL were retrospective study,which were divided into two groups of bi-SSNHL(n=40) and uni-SSNHL(n=440).Clinical characteristics and treatment effects were compared of the two groups.Result:The incidence rate of bi-SSNHL was 8.3 percent and uni-SSNHL was 91.7 percent of all patients with SSNHL. Bi-SSNHL occurs more commonly in patients of old age, diabetes mellitus, and lipid panes abnormalities compared to uni-SSNHL. Twenty-eight ears in the bi-SSNHL group showed hearing recovery (35%),compared with 56.4 percent of patients with uni-SSNHL.Conclusion:Bi-SSNHL and uni-SSNHL may have a completely different clinical characteristics and treatment effect,that implies a different pathophysiology and prognosis. Recognition their different clinical characteristics and treatment effect between bilateral and unilateral SSNHL can help in counseling and managing the patients and correctly evaluate the prognosis.