Urine estrogens were measured in 46 women students, ages 15–18, at a middle-class high school in Athens and in 40 women of the same age residing at one of three orphanages in the same city. The lower socioeconomic status (SES) of the latter group was documented by their lower mean height (by 5.2 cm) and weight (by 5.3 kg) relative to the high school students. Both in follicular and luteal phases of the menstrual cycle, the women with lower SES had 50% higher estriol ratios (ratio of the concentration of estriol to the sum of the concentrations of estrone and estradiol). In luteal specimens the concentration of all three major estrogens was higher in the group with low SES than in the women in the other group, but the concentration of estriol was most increased. There was also an indication of less frequent anovular cycles among the women with low SES. These findings are consistent with hypotheses linking either the estriol ratio or the frequency of anovular cycles to breast cancer risk.