Artificial perilymph containing kainic acid (KA) at various concentrations was perfused through the scala tympani in guinea pigs, and its effects on the whole nerve action potential (AP), cochlear microphonics (CM), summating potential (SP), endocochlear potential (EP), crossed olivocochlear potential (COCP), and cochlear ganglion-cell spontaneous activity studied. The administration of a 10 nmol dose of KA abolished AP but had little, if any, effect on CM, SP, EP or the COCP. The elimination of AP at this dose of KA appeared to be irreversible. Results obtained at lower doses (0.1, 0.25, 0.5, 1.0, and 2.5 nmol) suggested a very steep dose-response relationship in the action of KA. As expected, auditory nerve ganglion-cell recordings revealed the elimination of AP is most probably consequent to the suppression of afferent neural activity following an excitatory process. All these findings provide evidence that KA may exert a selective action on afferent nerve fibers and are consistent with the hypothesis that KA interacts with excitatory receptors located on postsynaptic membranes.