Primary mastoiditis is a rare disease involving mastoid antrum and air cells without involvement of tympanic cavity. The infection may have taken place though the hematogeneous route, from the middle ear into the mastoid with middle ear resolution apparently taking place while the mastoid infection continues. The first indication of otitic disease is the discovery of postaural edema. The authors have experienced a case of primary mastoiditis in a 62-year-old female patient for the first time in Korea. She had been suffered from severe left temporooccipital headache and retroauricular tenderness and swelling since 1 month before. The diagnosis was confirmed by simple mastoidectomy under the surgical microscope and biopsy. The postoperative course was quite favorable.