Pairs of very small electrodes were placed in two or more turns of the cochlea of the guinea pig. The cochlear microphonic from a short segment (about 1 mm) of the cochlear partition can thus be recorded, and without contamination by action potentials. The outputs of the second, third, and fourth turns were compared with that of the first turn with respect to both amplitude and phase as a function of frequency. The space‐time pattern thus revealed is a traveling wave which passes up the cochlea to a distance that depends on the frequency. The pattern agrees well with that of mechanical movement (Bekesy) except that the cochlear microphonic shows relatively greater amplitude (voltage) in the basal turn. Low frequencies travel farther up the cochlea than do high. The velocity (for a 750 cps tone) is about 100 m/sec in the basal turn and about 2 m/sec in the fourth turn. Phase differences of as much as 5π were observed, by means of Lissajous patterns, between the responses of the first and the third turn. Ce...