The dally excretion of estrone, estradiol, and estriol was determined for 22 normal women and 35 women with primary breast cancer. The excretion of the hormones (measured in µg/24 hr) in the breast cancer group was elevated and showed a statistical significance of P<0..001. The same wide difference between the 2 groups was also noted when excretion was expressed In terms of the body area of the Individuals and when women of similar ages were compared.