The efferent auditory fibers are originated from many different sites in the central nervous system. From the superior olivary complex, they are projected to the cochlea through two different tracts: the medial olivocochlear tract, which comprises large myelinated neurons that innervate predominantly the outer hair cells, and the lateral olivocochlear tract, with unmyelinated neurons, that synapses with the inner hair cells. Although many researches tried to determine the real action of the efferent auditory pathways in the human hearing, the physiological mechanisms of interaction between the efferent and afferent auditory system are still unknown. With the discovery of otoacoustic emissions by Kemp in 1978, it was possible to physiologically observe the function of the efferent system, mainly through an acoustic contralateral stimulation. The aim of the present paper is to show the several functions of the efferent auditory fibers on the auditory system and its possible role in some symptoms such as tinnitus and hyperacusis.