OBJECTIVES: Evaluate the cost-effectiveness of addition one-year adjuvant trastuzumab therapy to  standard adjuvant chemotherapy in treatment of HER2 + breast cancer (BC) early stage from a societal perspective in a Russian setting. METHODS: We used a Markov state transition model to simulate adjuvant trastuzumab treatment in a hypothetical cohort of early breast cancer patients for lifetime horizon. Patients were treated with a combination of chemotherapy and 1-year trastuzumab therapy (HT + T) or only with chemotherapy (HT). The transition probabilities between states in the Markov model, the effectiveness and usefulness of treatment were obtained from clinical studies HERA, 2005 and other published data. Costs for each state Markov model based on the standard treatment of breast cancer in Russia. Data about cost of medical services and drugs are received from the price-list of out-patient medical aid in clinic MMA of I.M.Sechenov 10.01.2010, site minzdravsoc.ru//medicine and other accessible electronic resources. Costs, effectivenesses, utilities were discounted at 3%. Sensitivity analysis for key parameters in the model was conducted. RESULTS: On the basis of Markov model with lifetime horizon, CT+T has an incremental cost-effectivesness ratio (ICER) of  860.704 roubles per LYG and incremental cost-utility ratio (ICUR) of 986.015 roubles per QALY. According to our threshold analysis, additional expenses on additional QALY are in a comprehensible range (825.000 -1.650.000 roubles), that has allowed to make the conclusion about an acceptability of one-year use trastuzumab in treatment of patients HER2 + breast cancer at early stages. Sensitivity analysis showed that major factors influencing cost-effectiveness and cost-utility ratios are survival gain, price of trastuzumab, discount rates. CONCLUSIONS: The combination 1-year adjuvant trastuzumab with standard chemotherapy is more cost-effective and cost-useful in comparison with standard chemotherapy for patients HER2 + breast cancer at early stages.