This study reports the evaluation of hearing results after implantation of a Teflon piston of a different diameter in cases of otosclerosis requiring stapedotomy. By random selection, a Teflon piston with a shaft diameter of 0.3 mm was inserted in 34 cases and a piston with a shaft diameter of 0.4 mm in 26 cases. A retrospective analysis of the pre- and postsurgery audiological results of these two patient groups was carried out by microcomputer. A repeated statistical measures analysis of variance was used to test and estimate the air-conduction frequency-specific differences between the two prostheses with respect to changes in pre- and postoperative healing. The results of this comparative study of the two Teflon pistons with different diameters indicate statistically a greater hearing gain for the 0.4-mm prosthesis, especially in the lower frequencies.