Urine levels of three major estrogens and of pregnanediol were measured for 76 nulliparous daughters of breast cancer patients and for 115 control women of similar age and parity. Concentrations of estrone and estradiol tended to be higher in the daughters of breast cancer patients than in the controls; total estrogens were elevated in both phases than in the controls; total estrogens were elevated in both phases of the menstrual cycle and significantly so in the luteal phase. There was little difference between the daughters and the controls in estriol ratios--the ratios of the concentration of estriol to the sum of the concentrations of estrone and estradiol. Pregnanediol levels were higher in the daughters than in the controls.