Because racial/ethnic disparities in breast cancer survival have persisted, we investigated differences in breast cancer treatment among American Indian, Hispanic, and non-Hispanic White (NHW) women. Surveillance, Epidemiology and End Results data linked to Medicare claims in New Mexico and Arizona (1987-1997) among enrollees aged 65 and older were used to identify treatment, treatment interval, and mortality risk associated with delays in care. We identified 2,031 women (67 American Indian, 333 Hispanic and 1,631 NHW women with time to treatment information. Treatment intervals from diagnosis to surgery (all stages, 18 versus 4 days, p.