The short-term and long-term results of stapedectomy for eliminating the conductive element and improving the hearing in patients with otosclerosis are highly satisfactory all over the world. The delayed sensorineural hearing loss which continues after successful stapedectomy may be due to the operation itself or due to the natural history of the disease. The study was conducted on 80 patients with unilateral stapedectomy with a minimal follow-up period of 1 year. We found that bone conduction values at each frequency in operated ears were stable with marked improvement at 2,000 Hz, on the other hand, the bone conduction thresholds in non-operated ears significantly deteriorated (p < 0.001). The speech discrimination score was significantly improved in the operated group (p < 0.001). An explanation for the cochlear changes in operated and non-operated ears is presented.