It has been hypothesized that the ratio of urinary 2-hydroxyestrone to 16alpha-hydroxyestrone (2-OHE1/16alpha-OHE1 represents a biomarker for breast cancer risk; the lower the ratio the higher the risk. We obtained early morning urine samples from 70 'high risk' premenopausal women who had a first degree family history of breast cancer and 27 'low risk' women with no such history. Five estrogen metabolites in urine were determined: 2-OHE1, 16alpha-OHE1, estrone (E1), estradiol (E2), and estriol (E3) conjugates. We compared geometric mean levels of each metabolite adjusted for age and weight. 'High risk' women did not have elevated levels of any of these metabolites. Instead, we observed decrements of 3-27% in women with a family history of breast cancer compared with women without such history, this difference was statistically significant for E2, 2- OHE1, and 16alpha-OHE1. The ratio of 2-OHE1/16alpha-OHE1 was identical in women with and without a family history of breast cancer. These results were unchanged, when additionally adjusted for recent intake of alcohol or cruciferous vegetables. Our data suggest that among premenopausal women, family history is not associated with higher urinary estrogen levels or a lower ratio of urinary 2-OHE1/16alpha-OHE1.