Several reports in the literature have represented the sensitivity of the alternating cochlear potential as being easily degraded by cooling. Our attempts to replicate these findings in the guinea pig failed to confirm them; hence we have conducted a thorough investigation in which careful attention was given to (1) optimal physiological condition of the preparation, (2) accurate quantification of sound, and (3) precise measurement of intracochlear temperature. At low levels of cochlear output (1–10 μV) the sensitivity of the normal cochlea was found to be invariant down to at least 30° C. This invariance does not appear to hold for the cochlear output at higher levels, close to bendover. Possible theoretical implications of these findings are discussed.