Mallory bodies (MBs) are characteristic morphologic features of alcoholic hepatitis but are also associated with non-alcoholic liver diseases including long lasting cholestasis, metabolic and neoplastic disorders. MBs contain in addition to keratins non-keratin components, including microtubule-associated (tau protein) and other not yet characterized proteins in an aggregated form. Aggregation of these components in the cell is promoted by posttranslational modifications, such as partial proteolysis, phosphorylation and cross-linking, and may result in functional and structural disturbances of the cell depending on the physiologic function of the components involved. Several enzymes responsible for these modifications are Ca(++)-dependent. Thus, disturbance of Ca(++)-homeostasis may play an essential role in the pathogenesis of MBs. In some structural aspects MBs closely resemble inclusions associated with degenerative disorders of the central nervous system, including Alzheimer's and Parkinson's disease. Studies on the pathogenesis of MBs, therefore, not only shed light on a peculiar type of liver cell injury but may also assist in the understanding of other chronic degenerative diseases, particularly those of the central nervous system.