OBJECTIVES: Identify differences in diagnosis and treatment of commercially insured White and African-American women with newly diagnosed breast cancer. METHODS: We conducted a retrospective, observational analysis of a Southeast US health plan’s administrative claims data linked to Georgia Comprehensive Cancer Registry (GCCR) data from 1/1/04 to 12/31/07 on newly diagnosed African-American and White breast cancer patients. Medical and pharmacy utilization data were obtained from the claims.  Cancer characteristics such as diagnosis date, Estrogen/Progesterone Receptor (ER/PR) status and race were obtained from the GCCR.  Patients without race data or coded as other races were removed for a final sample size of 1,497.  Descriptive analyses were conducted with t-tests for continuous variables and chi-square for categorical variables.  Multiple logistic regression determined factors associated with lower use of anti-estrogen therapy among African-American women. RESULTS: When comparing African-American to White women, African-American women were younger at diagnosis (mean age: 50 vs. 53 years, p<0.01), were diagnosed at later stages of breast cancer (Stage 0: 20% vs. 21%; Stage 1: 30% vs. 38%; Stage 2: 30% vs. 27%; Stage 3: 10% vs. 7%; Stage 4: 5% vs. 1% and unknown stage: 6% vs. 5%, p<0.01), and had a longer time to treatment (surgery: 57 vs. 42 days, p=0.01; radiation: 177 vs. 138 days, p<0.01; anti-estrogen therapy: 211 vs. 180 days, p=0.07).  Among women who were ER/PR-positive, White women were more than twice as likely as African-American women to be treated with anti-estrogen therapy (OR = 2.24, 95% CI: 1.46-3.43), after controlling potential confounders. CONCLUSIONS: This study demonstrates that diagnosis and treatment of breast cancer in African-American women differ from that of White women despite having access to commercial insurance.  We also illustrate that data linkages provide quick and efficient methods for assessment of cancer treatment patterns and identification of targets for further research.