The relationship of the inner ear to host immunity and the immunoresponsiveness of the inner ear to antigen challenge were investigated. A radioimmunoassay was used to quantitate antibody titers to keyhole‐limpet hemocyanin generated in the serum, perilymph, and CSF of guinea pigs following systemic or inner ear immunizations. The results of these experiments demonstrate (1) the blood‐labyrinth barrier is analogous to the blood‐brain barrier with respect to immunoglobulin equilibrium, (2) the inner ear is capable of responding to antigen challenge, and (3) the inner ear is an effective route for systemic immunization.