Simultaneous auditory processing between the hemispheres was studied with a whole-head magnetometer in 13 abstinent chronic alcoholics and 10 healthy control subjects. Auditory stimuli were presented monaurally with interstimulus intervals of 0.5 and 2.5 sec in different blocks. The N100m response, which contributes to stimulus detection, was significantly accelerated in the hemisphere ipsilateral to the ear stimulated in abstinent alcoholics. The MMNm response reflecting automatic stimulus-change detection peaked earlier in alcoholics, and the ipsilateral N100m latency correlated significantly with the abstinence duration. These results suggest that auditory processing is accelerated in the auditory cortex ipsilateral to the stimulated ear in chronic abstinent alcoholics and that the accelerated processing is at least partly reversible. This may be caused by the hyperexcitation in the brain related to the ethanol withdrawal.