Objective: The Purpose of present study is to evaluate the effect oftemporomandibular joint (TMJ) bony ankylosis and its relevant gaparthroplasty on the auditory functions.Patients and Methods: Pure tone audiometry, tympanometryand CT scan of middle ear volume were utilized as calipers forassessment of auditory functions in ankylotic patients and after surgeryof gap arthroplasty. Eight ankylotic patients have been managed by gaparthroplasty.Results: Some degree of hearing impairment has been detectedpreoperatively in TMJ bony ankylosis patients. A deficient middle earvolume has been detected. Negative values of tympanic peak pressurehave been advocated preoperatively and certain improvement has beendetected at the end of follow up with a positive values.Conclusion: Gap arthroplasty combined with jaw mobilizationapplied in the current investigation and improvement of swallowingmechanism help in aeration of middle ear via Eustachian tube. Gaparthroplasty has no deleterious effects on hearing quality.