The occurrence of 3 tar cancers of the skin, 1 uterine cancer, and 1 gastric cancer are reported in rats fed with an estrin product obtained from pregnancy urine. A tar cancer is recorded in 1 control rat. Whereas in rats injected with estrone for long periods, carcinoma of the genital tract and breast occurred accompanied by other usual estrin effects, it appears that with prolonged injection of testosterone, the females went into permanent vaginal diestrus, the pituitary weights were not above normal limits, somatic growth was not inhibited, and the predominant neoplastic lesions were fibrous tissue tumors in injected areas, some of which became sarcomatous.