OBJECTIVES: Evidenced-based guidelines for the treatment of breast cancer have been put forth by agencies such as the National Comprehensive Cancer Network (NCCN). Yet, even with specific guidelines, gaps in the receipt of appropriate care exist. This study examined factors associated with receipt of appropriate vs. inappropriate treatment among elderly women with breast cancer in the U.S. METHODS: A sample of 11,948 women age > 66 with pathologically staged I, II, and III breast cancer diagnosed from 2004 to 2006 were selected from the SEER-Medicare linked dataset. Algorithms based on clinical cancer characteristics and types of treatments and testing received were used to determine appropriateness of care (yes vs. no). Logistic regression models were used to examine the relationship between appropriateness of care and various independent factors. RESULTS: Less than 32% of elderly women received guideline appropriate care. The likelihood of receiving appropriate care decreased for women with increasing age (>80 vs. 66-69) (AOR, 0.23; 95%CI, 0.20-0.27), comorbidity (>2 vs. 0) (AOR, 0.85; 95%CI, 0.75-0.97), stage (III vs. I) (AOR, 0.50; 95%CI, 0.40-0.61) and (II vs. I) (AOR, 0.33; 95%CI, 0.28-0.38), and were of non-white race vs. white (AOR, 0.83; 95%CI, 0.73-0.96). Women with node negative cancer, poorly differentiated tumors, borderline/unknown tumor receptors were also less likely to receive appropriate care. Yet, the likelihood of appropriate care was increased for women who saw both a general and oncology surgeon vs. general surgeon only (AOR, 1.35; 95%CI, 1.19-1.53), lived in areas of higher income vs. lower (AOR, 1.15; 95%CI, 1.01-1.30), and higher education vs. lower (AOR, 1.15; 95%CI, 1.03-1.29)