A technique has been developed whereby the average composition of a liver cell can be calculated from the results of a detailed chemical analysis of a sample of liver tissue. The number of cells in a unit weight of the sample is determined from its content of deoxynucleic acid with corrections for polyploidy and for the presence of binucleate cells. This technique has been employed to determine the amounts of the principal cellular constituents in the cells in the livers of normal male and female rats. The cells of the two sexes did not differ greatly in composition except that the female cell contained about three times as much iron as that of the male. The analysis of nuclear suspensions showed that copper was almost exclusively confined to the nucleus, whereas iron and zinc were almost entirely in the cytoplasm. The sizes of the cells and of their nuclei deduced from the determination of their composition were in good agreement with results of histological determinations of other workers.