The crossed olivocochlear bundle (COCB) was stimulated with biphasic pulse trains while recording the cochlear summating potential (SP) with electrodes placed in scala vestibuli and tympani of either the first, second, or third cochlear turns of 21 guinea pigs. The outputs of the two electrodes were subsequently added (AVE SP) and subtracted (DIF SP) so that various components of the SP could be analyzed. It is shown that the DIF SP was consistently altered in a positive direction in all three cochlear turns at all frequencies and intensities during efferent activation. The greatest relative COCB effect for the DIF SP was achieved when it was recorded at low intensities and from the second and third turns of the cochlea. Both AVE SP components were significantly decreased in magnitude when recorded from the first turn during COCB stimulation. Data collected from turns two and three suggested that the efferent system exerts a strong positive influence on the overall AVE SP response. The results suggest that the efferent influences on the SP are consistent with models of COCB action on hair cells. Further, the findings conform to what would be predicted by other biasing techniques, and therefore it is recommended that COCB stimulation be considered as a tool for studying the origin and function of the cochlear potentials.