In order to evaluate the effect of alcohol consumption and the effect of abstinence on central nervous system generated parameters, we performed pattern visual evoked potential (PVEP) recordings on chronic alcoholics. The study was conducted on forty patients diagnosed as chronic alcoholics according to DSM IV criteria. They were aged mean: 42, and had histories of alcohol abuse for at least six years (mean: 21). 15% of the patients demonstrated abnormal VEP results at least in one tested eye. In order to test the effect of abstinence period on P100 latency values, alcoholics were divided in to two subgroups. Group I (Gr I) consisted twenty-four alcoholics who had been abstinent for less than thirty days (mean: 14), and Group II (Gr II) consisted sixteen alcoholics who had been abstinent for more than thirty and less than seventy-six days (mean: 38) The mean P100 latency of Gr I and Gr II was 101 and 102 milliseconds (ms) respectively; and when compared to normal controls the difference was statistically significant (p: 0.016, p: 0.009). Abnormal VEP in asymptomatic chronic alcoholics suggests that they may be useful in the detection of early changes and in following the progress of patients with the disorder. (C) 2006 Elsevier Ltd. All rights reserved.