Sensorineural hearing loss is an important complication of mumps. Audiologic tests of 26 children with mumps meningoencephalitis, 25 uncomplicated mumps cases and 20 control cases were performed, and hearing level thresholds at speech and high frequencies were determined. The mean hearing level thresholds in the mumps meningoencephalitis group were higher than those of mumps cases at frequencies from 6000 to 18 000 Hz in the right ear and at 250 and from 4000 to 18 000 Hz in the left ear (P < 0.05). Mumps meningoencephalitis cases had higher mean hearing thresholds than did control groups at all frequencies other than 125 and 250 Hz in the right ear and 10 000 Hz in the left ear. The mean hearing thresholds of mumps cases were higher than those of control group at frequencies of 1000 and 4000 Hz in the right ear and 1000 and 10 000 Hz in the left ear (P < 0.05). These results show that mumps meningoencephalitis causes a higher risk of hearing loss than does mumps.