Alcohol dehydrogenase 2 (ADH2) and mitochondrial aldehyde dehydrogenase 2 (ALDH2) are the major enzymes involved in oxidative degradation of ethanol, and they catalyze the conversion of ethanol to acetaldehyde and further into acetic acid. The frequencies of ADH2^*2 and ALDH2^*2 varied across ethnic groups and the distortion frequencies were shown in alcoholics. We examined the exon 3 of the ADH2 and exon 12 of the ALDH2 genotypes by PCR-RFLP from 53 alcoholics and 232 controls in Korean. The ADH2^*1/ADH2^*1 homozygote was significantly predominant in alcoholic patients (45.3%) compared to control subjects (6.0%) (p<0.001), whereas there was inverse relation in ADH2^*2/ADH2^*2 (p<0.001). The ALDH2^* 1/ALDH2^* 1 homozygote was 94.3% for alcoholics compared with 75.9% of controls (p<0.001). All alcoholics had AL DH2^* 1 allele in our study. The high relative risks for alcoholics were found in ALDH2^* 1 and ALDH2^* 1 and their relative risks (R.R.) are 2.9 and 8.1, respectively. On the other hands, the allele frequencies of ADH2^* 2 and ALDH2^* 2 for alcoholics were lower than those of controls. These data suggest that ADH2 and ALDH2 gene polymorphisms may be associated with tloe development of alcoholics in Korean. Same genetic predisposition to alcoholics was shown in other Orientals (Japanese and Chinese) but not in Caucasians.