Evidence suggests that the reliability of urinary androgens or estrogens as prognostic discriminants for breast cancer may vary with different populations and may bear little relation to changes in plasma hormone levels. In this study the plasma estradiol level was significantly lower in Bantu, but did not in Caucasian, women with breast cancer, while the proportion of plasma androstenedione to dehydroepiandrosterone increased in Bantu patients. These changes in the plasma hormone profile in Bantu patients, a low-risk population for breast cancer, imply a change in ovarian and/or adrenal activity. Lack of similar hormone changes in Caucasian patients may be due to the initial differences in the hormone profile between the healthy Caucasian and Bantu women and to the different environmental factors that promote the breast disease in Western women.