OBJECTIVES: To study initial treatment and survival among elderly patients with newly diagnosed Stage IV breast cancer, by estrogen receptor (ER) and progesterone receptor (PR) status. METHODS: The linked Surveillance and Epidemiology End Results-Medicare (SEER-Medicare) database was used for this analysis.  We identified female patients newly diagnosed with Stage IV breast cancer in a SEER registry between January 2002 and December 2007.  Study patients were required to be aged 66+ years with no prior history of any other (non-breast) cancer.  Patients were followed from the date of breast cancer diagnosis through death or December 31, 2009. Patients were identified as having positive (negative) ER or PR status if the corresponding assay was reported to SEER as positive/elevated (negative/normal).  Demographics, initial treatment (surgery or radiation within 4 months of diagnosis), and survival (Kaplan-Meier [KM] survival curves) were evaluated, by ER and PR status. RESULTS: A total of 3210 female Stage IV BC patients (2,417 [75.3%] ER+, and 793 [24.7%] ER-) were identified.  Of these, 57.5% were ER+PR+, 17.8% were ER+PR-, 1.4% were ER-PR+, and 23.3% were ER-PR-.  Age at diagnosis was similar regardless of ER/PR status (mean [SD] 74-77 [6-7] years).  Almost one third of patients had radiation (30%) and close to half of patients had surgery (43%) in the first 4 months following diagnosis, with slight variation by ER/PR status.  KM survival analyses suggest that ER+ patients had significantly higher median survival than ER- patients (24 months vs. 9 months, P<0.01).  Median survival was highest for ER+PR+ patients (25 months) followed by ER+PR- (19 months), ER-PR- (9 months), and ER-PR+ (7 months). CONCLUSIONS: Among elderly, newly diagnosed Stage IV BC patients, those with ER+PR+ status had the best survival outcomes.  Further studies of treatment patterns and outcomes by ER and PR status are warranted.