It has been reported that age-specific breast cancer rates vary by estrogen receptor and progesterone receptor status. We report breast cancer rates for age-at-diagnosis, stage-at-diagnosis, histological grade and type by estrogen (ER) and progesterone (PgR) receptor status in six major racial/ethnic groups. The average annual age-adjusted rates for breast cancers with estrogen receptor positive (ER+), ER-, progesterone receptor positive (PgR+), PgR-, ER+PgR+, ER+PgR-, ER-PgR+ and ER-PgR- are determined from 123,732 breast cancers with known ER status, diagnosed from 1992 to 1998 from 11 Surveillance, Epidemiology, and End Results (SEER) cancer registries. For each racial/ethnic group, their ER+ (ER+PgR+ and ER+PgR-) age-specific rates increased with age (but at a slower pace after ages 50-54) while their ER- (ER- PgR+ and ER-PgR-) age-specific rates did not increase after ages 50-54. The rank orders of the rates among the racial/ethnic groups varied by ER/PgR status. The stage I rates were greater than the stage II rates for the ER/PgR groups except for ER- and ER- PgR- cancers. The grade 2 (moderately differentiated) rates were greater than the grades 3 and 4 (poorly differentiated and undifferentiated cancers) rates for ER+ cancers, but not for ER- cancers. These results suggest that although breast cancer is a disease with enormous heterogeneity, the multiple types of breast cancer can be separated into distinct subgroups by their ER status, and perhaps by their ER/PgR status, and their cancer characteristics may be important in understanding the multiple nature of breast cancer.