Measurements according to the polarographic principle in cats have shown that the factors influencing the perilymphatic oxygen tension are the arterial PCO2, the arterial PO2, and the systemic blood pressure. In patients with sudden deafness, the oxygen supply to the vestibular tissues is significantly reduced but the response to carbogen is still possible. The vasodilation induced by carbogen in sudden deafness is not accompanied by a reduction (stealing effect) but by an increase of perilymphatic oxygenation. Therefore carbogen inhalation was used for the treatment of sudden deafness. In a prospective randomized study, carbogen inhalation yielded significantly better results than the intravenous infusion of papaverine and low-molecular dextran. Carbogen inhalation is recommended for the effective, noninvasive treatment of sudden deafness.