The causes of sudden sensorineural hearing loss are still obscure in spite of many studies. Since McCabe's first description of autoimmune sensorineural hearing loss in 1979, there were several reports of Immunologic study in inner ear diseases by many authors. For the significance of sudden sensorineural hearing loss and autoimmune sensorineural hearing loss, the authors studied 16 patients who were diagnosed as a sudden sensorineural hearing loss about immunologic assay including erythrocyte sedimentation rate(ESR), C-reactive protein, rheumatoid factor, VDRL, immunoglobulin and complements. The following results were obtained. 1) ESR was increased in 31.3% of cases. 2) C-reactive protein and rheumatoid factor were responded in 18.8%, 12.5% of cases each. 3) Ig E was elevated in 31.3% of cases. 4) C4 was elevated in 6.3% of cases, and C1q was decreased level in 81.3% of cases.