The present electrophysiological study was done to confirm an expected low‐tone dysfunction in guinea pigs poisoned with cumulated doses of methylmercury. Forty young‐adult Hartley strain guinea pigs were fitted stereotaxically with permanent recording electrodes having tips in the auditory tubercle and on the dural surface of the cerebrum. Twenty animals were injected subcutaneously with cumulated doses (2 mg/kg/day) of methylmercury chloride solution five times per week for periods ranging from 10 to 38 days. Twenty control subjects were injected with comparable volumes of sterile water. Click‐ and pure‐tone‐evoked responses were recorded during the waking state using a summing computer. Neither input‐output functions nor visual detection levels for tones from 0.125 through 16 kHz provided any evidence for low‐tone dysfunction in methylmercury‐treated subjects. Supranormal evoked response amplitudes were seen at 8 and 16 kHz. Contrary to earlier conclusions based only on morphological data, the guinea pig as a species appears to be an inappropriate model for methylmercury‐induced deafness reported in human victims.