Neither otomycoses nor defects of the tympanic membrane are rare. In cases of fungal infection when the tympanic membrane is not intact, the possibility exists that antimycotic medication could enter the middle ear and diffuse into the cochlea via the round window. Five antimycotic preparations were tested for acute ototoxic potential in guinea pigs. Those containing acetic acid or propylene glycol caused appreciable elevation of brainstem response thresholds, while little or no impairment resulted from tolnaftate or clotrimazole solutions in polyethylene glycol 400.