There is a long history of controversy concerning the locus and mechanism of harmonic‐distortion processes in the cochlea. This controversy has importance for theories of frequency analysis along the basilar membrane and concepts of the transduction process in the hair cells, as well as for the clinical significance of psychophysical tests of aural harmonics. The cochlear‐microphonic response to a pure tone recorded at the round window of the guinea pig was led into three wave analyzers tuned to the 1st‐, 2nd‐, and 3rd‐harmonic frequencies, each component then driving one channel of a pen recorder. The various components exhibit shifts through time, which were studied at various frequencies and intensities, and during recovery from fatiguing and damaging levels of tonal and random‐noise stimulation and anoxia. The data are discussed in terms of mechanical versus transduction concepts of harmonic distortion in the cochlea.