Acetaldehyde covalently binds to purified tubulin in vitro to form both stable and unstable adducts. The formation of stable adducts can be greatly facilitated by the inclusion of the relatively gentle and Schiff base specific reducing agent, sodium cyanoborohydride. Although the tubulin molecule has multiple lysine resides available to react with acetaldehyde, certain key lysine residues on the alpha-chain appear to be selective targets for adduct formation. The formation of alpha-chain specific stable acetaldehyde-tubulin adducts results in functional impairment of the ability of tubulin to polymerize. Under relatively physiologic conditions where acetaldehyde-to-protein ratios are low, alpha-chain specific binding is prominent. These results, coupled with the studies presented in another report in this volume, raise the possibility that low levels of adduct formation may be detrimental to the structure or function of certain proteins (e.g. tubulin) in the liver. The alteration of this or other biologically important proteins by sustained low levels of adduct formation may contribute to the pathogenesis of alcoholic liver injury.