Conventional electrophysiological technique was used to investigate the influences of electrical stimulation to medial prefrontal cortex (mPFC) on the acoustically evoked responses of auditory cortical (AC) neurons in 40 rats. Among 122 AC neurons isolated, the influences of mPFC on the acoustically evoked responses of 93 AC neurons were investigated systematically. 20 (21.5%) neurons were not affected, but the acoustically evoked responses of the remaining (73 neurons, 78.5%) were either facilitated (39 neurons,41.9%) or inhibited (34 neurons, 36.6%). The degree of facilitation and inhibition in the acoustically evoked responses was dependent upon the time intervals between acoustic and electrical stimuli. The best intervals of facilitation or inhibition were between 5 and 30 ms (mostly 10 and 15 ms). Our findings suggest that the mPFC may affect the activity of AC neurons through different multi-synaptic pathways.