Ototoxicity is probably the least acknowledged adverse reaction of erythromycin. The mechanism of erythromycin ototoxicity is still unknown. Here we report on two new cases of erythromycin-induced hearing loss. In both of them, serial evoked auditory brainstem potentials (EABPs) were obtained. The recorded EABPs showed absence of waves I to III during treatment with erythromycin, and normalization of all EABP waves after the administration of erythromycin had been stopped. Our findings support the hypothesis that erythromycin-induced hearing loss is attributable to a functional disorder in the peripheral parts of the auditory system.