Double-blind studies were conducted for the treatment of idiopathic sudden hearing loss (ISHL) with oral steroids. The condition was defined as not less than a 30-dB loss over three contiguous frequencies in three days or less. Follow-up audiograms were obtained four weeks and three months later. Specific audiologic guidelines for the assessment of hearing recovery were used to ensure objectivity. Steroids had a statistically significant effect on the recovery of hearing in patients with moderate hearing losses. The nature of the hearing loss and its susceptibility to improvement with steroid therapy lend support to the hypothesis that viral cochlitis is the primary cause of ISHL.