Alcohol metabolism is a complex process with large individual variations related to absorption, distribution and elimination. Among the multiple factors which influence these variations, genetic factors especially those related to the different alleles of ADH2 and ALDH2, are the most well known and are related to the development of alcohol dependence, particularly in some populations such as those of Asian origin. The importance of new polymorphisms such as those in the ALDH promotor region requires further study. Furthermore, the importance of other factors such as nutrition and gastric metabolism should be taken into account to explain the variations in ethanol metabolism. The metabolic alterations produced by alcohol in the liver are responsible for liver damage. The individual variations in the metabolism of alcohol are responsible for the different toxicity of alcohol in both the liver and other organs.