Background & Objectives: Otosclerosis is one of the causes of conductive hearing loss in different ages, the diagnosis of which sometimes becomes difficult using clinical and audiological symptoms. The early diagnosis and surgical treatment of this disorder will give a normal hearing to the patient. The goal of this study was to determine the role of exploratory tympanotomy in revealing the patients with hearing loss as a result of otosclerosis which is impossible to be diagnosed based on clinical and audiological, symptoms.

 Methods: This prospective study was conducted on 33 patients (18 females and 15 males) with conductive hearing loss suspected to otosclerosis, who were admitted to oto-rhino-laryngology department of Imam Khomeini hospital from 1999 to 2003 and underwent exploratory tympanomy. In 30 patients (16 females) otosclerosis was revealed during operation all of these patients underwent stapedectomy. During three weeks after surgery, the patients were examined in terms of facial paralysis, non-response to treatment, deterioration of hearing ability, dizziness, the probability of tympanic perforation and other complications. Audiological tests were also studied. The obtained data were recorded and compared with findings of other researches.

 Results:�The prevalence of the disease in women was more than men, and the majority of the patients had referred to be treated in the third and fourth decade of their life, while they had a history of hearing loss from the second or third decade of their life. The positive family history was below compared to other studies, but conductive hearing loss was more prevalent. This treatment led to hearing improvement in majority of the patients.

 Conclusions: Considering the proper time for stapedectomy is very important since better results can be abtained if the patients are operated with lower degrees of hearing loss. Thus, exploratory tympanotomy leads to early diagnosis and treatment in patients with conductive hearing loss suspected to otosclerosis.