Authors studied for the structure of the chorda tympani nerves which were sacrificed while performing surgical procedure in eighteen patients with chronic otitis media. The structure of the chorda tympani nerves was observed using light and electron microscopes, and analysis about gross anatomy, fiver number, myelin sheath, axoplasm and so forth was performed. The obtained results were as follows : 1) The chorda tympani nerve covered with epineurium was consisted with many fascicles ensheathed with perineurium, and also vessel was located at central or peripheral portion of the chorda tympani nerve. 2) The number of nerve fibers ranged from 2,020 to 6,361 with average of 3,564. 3) The fibers of the chorda tympani nerves in patients with chronic otitis media without cholesteatoma were structurally intact, but the thickening of epineurium was observed in a case. 4) The fibers of the chorda tympani nerves in patients with chronic otitis media with cholesteatoma were structurally intact except a case in which degenerative changes such as multiple vacuoles in axoplasm and Schwann cells were observed, and also the thickening of epineurium was observed in three cases.