We investigated the effectiveness of Lipo-prostaglandin E1 (Lipo-PGE1) into patients with idiopathic sudden hearing loss. Thirty three patients were treated with steroids only (steroids group) and 40 patients were treated with steroids plus Lipo-PGE1 (steroids plus Lipo-PGE1 group). There was no significant difference in sex, age, initial hearing level, and period between the onset of the disease and the start of the treatment between the two groups. The rate of complete recovery and marked improvement was 45.4% in the steroids group and 65.0% in the steroids plus Lipo-PGE1 group at the final examination. There was no significant difference in the rate between the two groups. For patients under 60 years of age and those with vertigo in the steroids and Lipo-PGE1 group a significantly better outcome was seen in the rate of complete recovery and marked improvement. These results suggest that the Lipo-PGE1 may be effective as a concomitant drug with the steroids regardless of the age and hearing level of the patient for the treatment of idiopathic sudden hearing loss.