Previous research has documented racial/ethnic disparities in breast cancer survival, these data alone are limited in their lack of specificity and availability of key variables, including full course of treatment and socioeconomic status (SES). A consideration of multiple social and clinical factors, and their interactions is necessary for understanding the multi-factorial causes of disparities, particularly as race/ethnicity is widely perceived to be a concept reflecting biological, socioeconomic, cultural, health access, and genetic factors. The ability to address all of these factors at once would depend on the availability of high quality data on these factors for a large and representative population. The enrichment of SEER data with high quality clinical data from the Henry Ford Health System (HFHS) and the Northern California Kaiser Permanente Medical Care Program (KPMCP), both members of the NCI-funded CRN), and neighborhood data on SES and health care access, would provide that opportunity. Thus, our proposed study has the potential to make significant headway into enhancing our understanding of the causes of the long-standing disparities in breast cancer survival. Study Objectives This study is funded as a multi-site collaborative study. Detroit will be the coordinating site working closely with the registry personnel at NCCC and will be responsible for managing the collaboration including the pooling of data, ensuring data comparability and quality across the sites, establishing the analysis plan, conducting the analysis of the pooled data, and managing the production, reporting and publication of study results.