To define better the benefits and risks of intratympanic gentamicin injection treatment of intractable vertigo or drop attacks due to Ménière's disease, we reviewed the charts of 18 patients whom we have now observed for > 1 year after having completed this mode of therapy. There were nine women and nine men aged 29-81 years; all had poor hearing in the affected ear. Of the 18 patients, 14 have had no further vertigo or drop attacks (11 patients after a single set of three to five injections, another three after a further set of one to five injections). The treatment could be effective even if it did not abolish caloric responses from the treated ear, even if it did not produce an acute vestibular deafferentation syndrome afterwards, and even after a failed vestibular nerve section. After treatment, five of the 18 patients developed oscillopsia and ataxia--symptoms and signs of (presumably permanent) chronic vestibular insufficiency; this proportion is not obviously lower than that after vestibular neurectomy or surgical labyrinthectomy. Of the 18 patients, 12 showed no change in the 1-kHz threshold and 13 showed no change in the 4-kHz threshold. When hearing did deteriorate, the threshold rose by more than 30 dB at 1 kHz in four patients and at 4 kHz in six patients. We conclude and confirm that intratympanic gentamicin injections are a convenient and, in most cases, effective and safe treatment for intractable vertigo or drop attacks due to Ménière's disease.