Approximately 50% of Asians experience a facial flush following alcohol ingestion. These individuals have an inactive form of mitochondrial aldehyde dehydrogenase (ALDH) encoded by the ALDH2*2 allele. This study matched 15 flushing and 15 nonflushing Asian men on demographics and drinking histories. The 30 subjects were genotyped for ALDH2 and were evaluated both before and following placebo and 0.75 ml/kg alcohol. The two groups did not differ significantly on blood alcohol concentrations after drinking, but did differ in electroencephalographic (EEG) response on the falling phase of the blood alcohol curve. Nonflushing subjects displayed significant increases in slow-alpha EEG activity (7.5-9.0 Hz) at 90 and 150 min post-alcohol consumption, compared to flushing subjects who did not show characteristic increases in this frequency band at these timepoints. These data suggest flushers, those with at least one ALDH2*2 allele, have less of slow-alpha wave EEG response to alcohol than nonflushers with ALDH2*1/2*1 genotype.