OBJECTIVES: To evaluate the cost-effectiveness of anastrozole (1 mg/day) versus tamoxifen (20 mg/day) as adjuvant treatment for early stages breast cancer in postmenopausal women. METHODS: Cost-effectiveness analysis was performed. Markov model was built based on the results of ATAC and ARNO 95 studies. Two strategies of adjuvant therapy – initial therapy with anastrozole and switching to anastrozole after two years treatment with tamoxifen were evaluate in the model, total duration of adjuvant therapy followed in the model was 5 years. The time horizon was equal to patient’s life expectancy. RESULTS: The results demonstrated that initial adjuvant therapy with anastrozole is cost-effectiveness in patients with high risk of relapse and also in the group of patients younger then 55 years. The cost-effectiveness ratio in the basis variant (population included into ATAC-study, age at the start of adjuvant therapy – 65 years) was 1161.4 thousand Rub/QALY (€25,800/QALY). In early debut of cancer at the age of <55 years, the cost-effectiveness ratio was 728.8 thousand Rub/QALY (€16,200/QALY). From the economic point of view the effective therapy scheme is switching patients to anastrozole after two years of tamoxifen treatment. The cost-effectiveness ratio of this scheme is estimated from 624,6 thousand Rub/QALY (€13,900/QALY) in patients at the age of 55 years to 1209.7 thousand Rub/QALY (€26,900/QALY) in patients at the age of 70 years. In the basis variant (population included into ARNO 95-study age at the start of adjuvant therapy – 60 years) the ratio was 776.4 thousand Rub/QALY (€17,300/QALY). CONCLUSIONS: The switching the patients in postmenopause to anastrozole after two years of tamoxifen treatment may be considered reasonable from the economic point of view in Russia. The initial adjuvant treatment with anastrozole in patients with high risk of relapse, not belonging to elder age groups, is also economically reasonable.