A total of 178 male and 104 female white rats were fed levels of DDT ranging from less than 0.05 to 5,000 p.p.m. for periods ranging from 1 week to 14 months. Mortality was not appreciable, and no effect on growth was observed on rats fed levels of 400 p.p.m. or less. Liver weight was definitely increased in rats fed 400 p.p.m; but there was no evidence of increase at 200 p.p.m. or less. Rats stored DDT in proportion to dosage. Both sexes convert a portion of ingested DDT to DDE, but female rats store more DDT and much more DDE than males. Levels of 400 p.p.m. or less produced histological changes in the liver only. The changes in the parenchymal cells of the liver consisted of an increased deposition of fat, margination of cytoplasmic granules, hypertrophy of the cells, and most characteristic--the formation of complex, lipoid, cytoplasmic inclusion bodies termed 'lipospheres.' The authors are in general agreement with Laug and associates in regard to the presence of cellular alterations in the liver of rats fed DDT at levels as low as 5 p.p.m. in the diet.