Learning Objectives: Although necrotizing otitis externa is life-threatened disease, it is difficult to be diagnosed and treated. Several points for diagnosis and the results of treatment would be reported.

Necrotizing otitis externa is osteomyelitis of skull base originated from the floor of external auditory canal. Most of them are optimizing infection, mainly DM. Main pathogen is Pseudomonas Aeruginosa. Although clinical features are clear, it is difficult to reach a correct diagnosis. Symptoms are sometimes masked by anti-biotics and analgesic drug. Severe pain, patient background such as DM, and granulation formation could be clue for suspicion. Both CT and MRI are useful for diagnosis and estimation for the extent of disease. Biopsy leads to definite diagnosis. First ling of treatment is conservative approach. Appropriate antibiotics should be chosen and patient backgroud disease would be controlled. Surgical intervention is useful when well-pneumatized mastoid is infected.