To evaluate the technical and functional results of 144 stapedotomies in patients with severe to profound hearing loss (SPHL) and to compare the success rate in this group with that of 1001 primary stapedotomies for mild to moderate hearing loss (MMHL).Retrospective chart review.Tertiary referral centre.The charts of 1369 consecutive stapedotomy cases were reviewed. One hundred twenty-seven patients (144 stapedotomies) with SPHL were included. The outcomes were analyzed according to the 1995 American Academy of Otolaryngology-Head and Neck Surgery Committee on Hearing and Equilibrium guidelines and evaluated with the Amsterdam Hearing Evaluating Plots and the Glasgow Benefit Plot.The magnitude of hearing improvement was greater in patients with SPHL compared with patients with MMHL. The mean gain in air conduction in patients with SPHL was 32 (+/- 13) dB compared with 23 (+/- 11) dB in the series of 1001 primary stapedotomies for MMHL. Air-bone gap closureor = 10 dB was achieved in 63% of cases andor = 20 dB in 90% of patients with SPHL, compared with 82% and 97%, respectively, in patients with MMHL.SPHL in otosclerosis is not infrequent, comprising 13% of all primary stapedotomies in this series. The magnitude of hearing improvement poststapedotomy is greater in SPHL compared with MMHL. Symmetric hearing could be achieved in two-thirds of patients, and normal hearing can be achieved in selected cases.