This study reports the evaluation of hearing results after implantation of a Teflon piston (type CausseÒ ) and of a pure gold piston (K-pistonÒ ) both with a shaft diameter of 0.4 mm in cases of otosclerosis requiring stapedotomy. The most important difference between both stapes replacement prostheses is the weight: the gold prosthesis is three times as heavy as the Teflon prosthesis. During the period from January 1994 to December 1995 sixty-two Teflon pistons were inserted during primary stapedotomy and during the period from January 1996 to December 1997 sixty-six gold pistons were inserted. Retrospective analyses of the pre- and postsurgery audiological results of these two prostheses were carried out. The results were compared with regard to several audiometric parameters. It appears that the heavier gold prosthesis gives a greater gain in air-conduction thresholds and shows an advantage in the improvement of bone-conduction in the low-frequency speech range. However, the inter-group differences were not statistically significant after exclusion of technically unsuccessful operations. There were no significantly better improvements in air- bone gap closure to 10 dB or less between both prostheses but the rate of overclosure was considerably greater with the gold piston.