Inhibition of protein synthesis and disaggregation of polyribosomes are characteristic, early effects of many liver carcinogens. These effects may in special cases depend on direct, structural interaction of the added compounds with ribosomes. However, the inhibition is more typically associated with the metabolic oxidation of the compounds in the liver endoplasmic membranes. Reactive metabolites, formed in this process, may interfere with the controlled handling of information-carrying macromolecules at various cellular levels. The experimental data sugggest that the inhibition of the ribosomal activity under these conditions is not primarily due to a reduced synthesis or life-span of messenger RNA, but rather to a disturbed peptide chain initiation. The relation between early and late events in the carcinogenic process is discussed in terms of a gradual alienation of the cytoplasm under the influence of carcinogens.