Mastoid drilling can cause transient hearing loss in the contralateral normal hearing ear. A study was designed to evaluate hearing in the contralateral normal ear before and after the mastoid surgery in a longitudinal manner and find out the duration of this temporary hearing loss. Twenty-two patients requiring mastoid surgery in their diseased ears, having contralateral normal ear were included. Pure tone audiometry and otoacoustic emissions (OAEs) were utilized for baseline evaluation. OAEs were repeated during the immediate postoperative period and daily up to the 6th postoperative day. The amplitudes of the OAEs of contralateral normal ears were found affected immediately after surgery and progressive improvement was detected with full recovery at 72-96 h. None of the patients had permanent deterioration in OAE amplitudes. The burs used during mastoid surgery can cause temporary hearing threshold changes in the contralateral ears. This adverse effect recovers spontaneously within 72-96 h postoperatively.