Prepulse inhibition (PPI) refers to a decreasedresponse to a startling stimulus when another weakerstimulus precedes it. Most PPI studies have focused on thephysiological startle reflex and fewer have reported the PPIof cortical responses. We recorded local field potentials(LFPs) in four monkeys and investigated whether the PPIof auditory cortical responses (alpha, beta, and gammaoscillations and evoked potentials) can be demonstrated inthe caudolateral belt of the superior temporal gyrus(STGcb). We also investigated whether the presence of aconspecific, which draws attention away from the auditorystimuli, affects the PPI of auditory cortical responses. ThePPI paradigm consisted of Pulse-only and Pre-pulse ? Pulse trials that were presented randomly whilethe monkey was alone (ALONE) and while anothermonkey was present in the same room (ACCOMP). TheLFPs to the Pulse were significantly suppressed by thePrepulse thus, demonstrating PPI of cortical responses inthe STGcb. The PPI-related inhibition of the N1 amplitudeof the evoked responses and cortical oscillations to thePulse were not affected by the presence of a conspecific. Incontrast, gamma oscillations and the amplitude of the N1response to Pulse-only were suppressed in the ACCOMPcondition compared to the ALONE condition. Thesefindings demonstrate PPI in the monkey STGcb andsuggest that the PPI of auditory cortical responses in themonkey STGcb is a pre-attentive inhibitory process that isindependent of attentional modulation.