Cogan's syndrome (CS) is the association of acute nonsyphilitic interstitial keratitis and acute episodes of vertigo, tinnitus, and hearing loss. We have prospectively followed 6 patients with CS who were treated within 4 weeks after the acute onset of hearing loss. Within 1 to 2 weeks after the initiation of corticosteroid therapy, all 6 patients demonstrated improved hearing thresholds for pure tones and supra-threshold speech discrimination results. These patients have been followed an average of 2.5 years (range 0.25-9 years); all have only mild to moderate hearing impairment in the mid (1,000 to 2,000 Hz) and low (250 to 500 Hz) frequency sound ranges. Three of the patients have been tapered off steroids completely with no subsequent permanent decrement of hearing. Thus, early oral corticosteroid administration to patients with sudden hearing loss associated with Cogan's syndrome may preserve auditory function.