OBJECTIVESTo analyze the clinical characteristics and treatment results between bilateral (bi‐) and unilateral (uni‐) sudden sensorineural hearing loss (SSNHL).STUDY DESIGN AND SETTINGA retrospective study.METHODSThree hundred twenty‐four patients with SSNHL were classified into two groups; simultaneous bi‐SSNHL (n = 16) and uni‐SSNHL (n = 308). We compared clinical characteristics, medical history, hearing level, and treatment results between the 2 groups.RESULTSThe incidence of bi‐SSNHL was 4.9 percent of overall patients with SSNHL. Bi‐SSNHL occurs more commonly in patients of older age, with preexisting diabetes mellitus, and lipid panel abnormalities compared with uni‐SSNHL. Ten patients (62.5%) in the bi‐SSNHL group showed hearing recovery in 1 or both ears compared with 56.5 percent of patients with uni‐SSNHL. Only 12 (37.5%) of all 32 ears recovered in bi‐SSNHL, which was significantly lower than in uni‐SSNHL.CONCLUSIONBi‐SSNHL has a very low incidence and lower recovery rate than uni‐SSNHL. Recognition of similarities and differences between bilateral and unilateral SSNHL can help in counseling and managing the patients.© 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved.