Microphonic potentials were recorded from the cochleas of guinea pigs and chinchillas. It was observed that with intense pure‐tone stimuli, subharmonic potentials could be detected in the microphonic. These potentials possess high threshold (between 110 and 130 dB SPL), above which they immediately assume magnitudes that are commensurate with that of the fundamental. Increase in stimulus intensity above the threshold results in some increase in the magnitude of the undertones, but saturation and rapid decline follow within a 10‐ 15‐dB range. The most frequent subharmonic appears at one half the driving frequency, but the quarter‐frequency component is also common.