To the Editor.—In the September 1977 issue of theArchives(103:524-530), Dr Nadol described a series of patients with Meniere's disease in whom a positive fistula test (Hennebert's sign) was elicited, while a negative fistula test was present in a series of patients with vestibular schwannomas and in normal control subjects. In 1972, we investigated the usefulness of the fistula test in confirming the diagnosis of perilymph fistula. Horizontal eye movements were monitored on one channel of a dc-coupled Dynograph (Beckman), and a second channel recorded data from a pressure transducer. Positive and negative pressure (± 40 mm Hg) was introduced into a sealed external auditory canal via a Foley catheter. A positive fistula test (generation of nystagmus) was recorded in the following ears: six of 15 (40%) normal ears, two of five (40%) ears with endolymphatic hydrops, and 11 of 21 (52%) ears after stapedectomy. The test was