In order to determine the molecular size of the causative autoantigens of experimental autoimmune labyrinthitis, crude inner ear antigen was separated into 14 fractions and the constituent molecules were identified by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis using the Mini Whole Gel Eluter. The mean total protein recovery was , 66%. Sensitization with 55-65 kDa proteins induced the highest number of infiltrating cells among the fractions and sensitization with 38-45 kDa proteins induced the second highest number of inflammatory cells. These results suggest that 38-45 kDa and 55-65 kDa proteins are the causative autoantigens of experimental autoimmune labyrinthitis.