Lipomatous mixed tumors of the kidney or perirenal tissues are not rare and those in the latter situation are usually malignant. Although pure lipomas of the kidney are of frequent occurrence, liposarcoma of this organ appears to be rare. In a review of the literature Fischer, in 1911, found 58 instances of renal tumor associated with tuberous sclerosis. Of these cases, 3 reported by Vogt were called liposarcomas. A search of the literature pertaining to renal tumors has revealed but one instance of pure liposarcoma not associated with tuberous sclerosis. This case was reported by Hartwig. Hartwig's patient was a woman, aged thirty-six years, who had had an enlarged abdomen for eight years. Suddenly she became seriously ill and went into collapse. Exploratory operation, with removal of the right kidney and its contained tumor, was done the same day. The patient died shortly after completion of the operation. The mass, which weighed 3500 grams, was of variable consistence and lobulated. Foci of hemorrhage were present within the tumor. Small nodules resembling the large tumor were present in other parts of the kidney. Microscopic examination showed that the tumor was composed largely of pure adult adipose tissue, but scattered through it were cellular foci made up of spindle and round cells and fat-containing cells. Hartwig considered it a lipoma undergoing sarcomatous change.