High alcohol sensitivity among Asians is mainly due to a genetic polymorphism in the low Km aldehyde dehydrogenase (ALDH2) gene. Strong correlations between the ALDH2 genotype and alcohol sensitivity or alcohol drinking habits have been reported. Another prevalent polymorphism in the alcohol dehydrogenase beta-subunit (ADH2 gene) among Asians appears to modify skin flushing reactions after exposure to ethanol but does not influence alcohol drinking behavior. Both the ADH2 and ALDH2 genotypes have been significantly correlated with the risk of alcoholism. In a Japanese occupational population, a gene-environment interaction of the ALDH2 genotype and daily hassles scores for development of problem drinking behavior was observed. Habitual drinkers with the ALDH2*1/*2 genotype had higher frequencies of sister-chromatid exchange in cultured lymphocytes and higher 8-OHdG levels in polymorphonuclear leukocytes than those with the ALDH2*1/*1 genotype. Alcoholics and heavy drinkers with the ALDH2*1/*2 genotype have been shown to have significantly elevated risks for esophageal and multiple cancers in upper digestive organs than those with the ALDH2*1/*1 genotype. In Japan, bronchial asthma patients with the ALDH2*1/*2 genotype have been shown to have a significantly elevated risk for experiencing alcohol-induced asthma compared with the ALDH2*1/*1 genotype. Providing services to determine these genotypes would be of great help for each individual to make a plan for tailor-made health promotion.