OBJECTIVES: Anastrozole primary adjuvant therapy compared to tamoxifen significantly improves disease free survival (DFS) and time to recurrence (TTR) and significantly reduces distant metastases and contralateral breast cancers in PM women with hormone-receptor positive early BC. METHODS: We developed a Markov model describing the clinical history of PM women with early BC that projected improvements in lifetime life years gained (LYG), long-term costs, and cost-effectiveness of the adjuvant treatment with anastrozole compared to that with tamoxifen. The base case was a 64-year-old PM women with hormone-receptor positive BC submitted to mastectomy and without metastases. Transition probabilities came from the ATAC study and other major studies from the medical literature. The local management and costs of each health state was based on a Delphi panel according to the private healthcare perspective. Outcomes were discounted at 3% annually. Sensitivity analyses and a second order Monte Carlo simulation were performed. RESULTS: The lifetime horizon analysis showed: Anastrozole in comparison to tamoxifen increased life expectancy (LY) in 0,55 year; the incremental cost per LYG was R$ 27.693,36; the tamoxifen group expenses in comparison to the anastrozole group in recurrence states (loco-regional disease and metastasis) and with adverse events were respectively 17% and 16% higher. CONCLUSION: Improvements in DFS and TTR with primary adjuvant anastrozole in postmenopausal women with operable hormone-receptor positive breast cancer improves patient outcomes in terms of LYG with an acceptable cost-effectiveness ratio in Brazil.