In the present experiment, changes in compound action potentials of auditory nerve (CAP), cochlear microphonics (CM) and endocochlear potentials were observed when the calcium concentration of perilymph was reduced by means of perilymph perfusion, with the aim of analyzing how calcium was involved. Perfusion with Ca(2+)-free artificial perilymph reversibly suppressed both CAP and CM amplitudes, but did not alter the basic nonlinear properties of CAP I/O curve. Furthermore, the perfusion did not alter the EP and negative EP (n-EP) induced by anoxia but eliminated the fast change of EP with respect to turning on and off of intense sound. The mechanisms underlying the effects of calcium are discussed.