Long Periods of postoperative care and necessity for repeated cleansing of epithelial debris from the cavity are not unusual after open cavity mastoidectomy. Mastoid obliteration using cortical bone chips has been recommended in order to solve these problems since Palva(1973) introduced this technique. We analysed 90 cases of mastoid obliteration using cortical bone chips with the special reference to periods of postoperative care and cortical bone resorption, as compared with 60 cases of open cavity mastoidectomy.