Study summary: The current study examined the prevalence of the eight possible combinations of ER/PR/HER2 status in California breast cancer patients in conjunction with five-year survival. Breast cancer generally is categorized according to the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). The California Cancer Registry was used to classify 61,309 women with primary invasive breast cancer according to ER/PR/HER2 status and five-year relative survival was computed for all possible combinations of subtypes. Odds ratios (ORs) were estimated using multivariate logistic regression. Women who were younger than 50 at diagnosis, African American, Hispanic, of low socio-economic status, and/or with stage IV undifferentiated tumors were more likely to have breast cancer with an ER-negative subtype (ER-/PR-/HER2+ or ER-/PR-/HER2- (triple negative)). Asian Pacific Islanders also had increased odds of having the ER-/PR-/HER2+ subtype (OR = 1.41; 95% confidence interval (CI) = 1.26–1.57). Stage III tumors (OR = 1.25; 95% CI = 1.08–1.44) and stage IV tumors (OR = 1.58; 95% CI = 1.27–1.98) were more likely than stage I tumors of being ER-/PR-/HER2+. Stage IV tumors were much less likely to be of the ER-/PR-/HER2- subtype (OR = 0.54; 95% CI = 0.44–0.67). Poorly differentiated and undifferentiated tumors were found to be more than 20 times as likely as well-differentiated tumors to be hormone receptor negative. Survival was found to vary from 96% for hormone receptor-positive/HER2 negative breast cancer (ER+/PR+/HER2-) to 76% for hormone receptor-negative breast cancer (including both ER-/PR-/HER2+ and triple negative). The four subtypes found to have the poorest survival were all ER-. The authors recommend reporting breast cancer as an ER/PR/HER2 subtype and precisely documenting demographic and tumor characteristics.