THE INTEREST of otologists and audiologists during the last 20 years has focused very much on the problem of diagnosing and treating stapes fixation. Unfortunately, there is no single test that predicts when the conductive loss is due to stapes fixation. However, the actual type of lesion can be determined with a very high degree of confidence by combining the history, the otological findings, and conventional test results with other tests discussed in this paper. These other tests include the sound probe test, the Gellé test, the prosthesis test,1 tympanometry,2 stapes and tensor reflex tests.3 Report of Cases The problem can be illustrated by reviewing two cases with the kind of diagnostic problem often encountered. The first case (Fig 1, top) has a history of hereditary progressive hearing loss with a perfectly normal tympanic membrane, considerable air-bone gap in the tone audiogram, and the Carhart notch on