The incidence of breast cancer in the US is known to be higher among white than black women and among women of higher socioeconomic status (SES), but once a woman, either black or white, has the disease, she is more likely to have a recurrence and to die of breast cancer if she is of lower socioeconomic status. Explanations for these observed differences are varied and inconsistent making it clear that these reported differentials are not sufficiently understood. In understanding breast cancer in a multicultural setting, delay in diagnosis, follow-up, and treatment are frequently the focus of attention. However these factors do not sufficiently explain the observed differences between blacks and whites. A review of recent literature reveals an increasing focus on the role of SES in breast cancer etiology, and progression; however, the confounding of SES with race/ethnicity (black vs. white) contributes to the insufficient understanding of the effect of these two factors. This report will focus on the interplay between race/ethnicity and SES and their relative effects upon analyses of survival from breast cancer. Findings are based on prospective clinical trial data. SES factors have been associated with most of the known or suspected risk factors for breast cancer incidence and progression. In addition to race/ethnicity, SES is also associated with diet, lifestyle factors, physical characteristics, and tumor characteristics. Without controlling for other risk factors, the ratios of risk for blacks with respect to whites for disease-free survival and overall survival were 1.30 (95% CI: 1.04-1.61) and 1.42 (95% CI: 1.15-1.76), respectively. However, after controlling for patient risk factors, such as the number of positive lymph nodes, tumor diameter, estrogen receptor status and socioeconomic factors, these differences decrease and are not statistically significant. Socioeconomic status is associated both with race/ethnicity and estrogen receptor status. A loglinear analysis demonstrates that the apparent association of race/ethnicity with estrogen receptor status is mediated by socioeconomic status. An implication of this finding is that environmental and lifestyle components rather than genetic factors associated with race may explain the observed differentials between black and white breast cancer patients. Knowledge of environmental factors associated with SES have the potential for providing important clues about the prevention and control of breast cancer.