Additional administration of alpha-tocopherol acetate to S57Bl/6 mice and Wistar rats exposed to oral CCl4 under acute and subacute experimental conditions produced no appreciable effect on the frequency of cells with chromosomal aberrations. Additional administration of alpha-tocopherol acetate to S57Bl/6 mice exposed to CCl4 inhalation significantly lessened the frequency of somatic cells with chromosomal aberrations and the frequency of dominant lethals in sexual cells. This attests to a protective action of alpha-tocopherol acetate and confirms the data obtained by other research workers.