This paper is the last in a series of three investigating the role of cholinergic mechanisms in the auditory system by assessing the acute effects of nicotine, an acetylcholinomimetic drug, on aggregate responses within the auditory pathway. In a single-blind procedure, auditory responses were obtained from 20 normal-hearing, non-smokers (10 male) under two conditions (nicotine, placebo). The effects of nicotine on long-latency responses of the auditory system and on electroencephalograms are described in this paper. Results indicated that transdermal administration of nicotine to non-smokers significantly affects the afferent and efferent transmission of acoustic information, as well as enhancing cortical activation. Long-latency response amplitudes and electroencephalogram activity (dominant power and frequencies) were altered by acute doses of transdermal nicotine.