A number of systems that generate oxygen free radicals and reactive aldehydic species are activated by excessive ethanol consumption. Recent studies from human alcoholics and from experimental animals have indicated that acetaldehyde and aldehydic products of lipid peroxidation, which are generated in such processes, can bind to proteins forming stable adducts. Adduct formation may lead to several adverse consequences, such as interference with protein function, stimulation of fibrogenesis, and induction of immune responses. The presence of protein adducts in the centrilobular region of the liver in alcohol abusers with an early phase of histological liver damage indicates that adduct formation is one of the key events in the pathogenesis of alcoholic liver disease. Dietary supplementation with fat and/or iron strikingly increases the amount of aldehyde-derived epitopes in the liver together with promotion of fibrogenesis.