This paper studies the changes in speech discrimination following stapes surgery in patients with advanced otosclerosis. Two thirds of these patients showed a postoperative improvement in the discrimination score with obvious correlation with closure of bone-air gap. The results were slightly worse in comparison to those obtained on otosclerotic patients with good bone conduction. In advanced otosclerosis even a minimal impairment in bone conduction and/or an incomplete closure of the gap interfere with discrimination.