OBJECTIVES: Trastuzumab (Herceptin®) as an adjuvant treatment for patients with early stage HER2+ve breast cancer, following surgery, chemotherapy and radiotherapy has been shown to reduce disease recurrence by ~50% and the risk of death at 2 years by ~33% (Piccart-Gebhart 2005). The objective of this analysis was therefore to determine the cost effectiveness of 1-year treatment with trastuzumab following standard chemotherapy vs observation for patients with HER2+ve EBC in the Romanian setting from the National Health Insurance House perspective. METHODS: A five health states Markov model was developed, using published results from HERceptin Adjuvant trial. Overall survival of patients was simulated over a projected 45 years lifetime horizon. Utility values for health states and events were taken from published literature. Direct medical costs were included. Resource use was based on expert opinion from the two biggest oncology centers in Romania. Unit costs (2009) were derived from Romanian retail prices for drugs, diagnostic and monitoring tests and procedures, day-hospital and inpatient stays costs. Costs were discounted by 5%. Sensitivity analyses were performed. RESULTS: This analysis showed that the incremental cost per patient for adjuvant trastuzumab therapy would be 26,462 EUR on average. Benefit to the patient would be 3.11 QALY, on average, in a 45 years time horizon. The incremental cost per QALY gained for adjuvant trastuzumab versus observation would be 8,498 EUR. Sensitivity analysis for different scenarios (0% costs and outcomes, 5% costs and outcomes, 5% costs and 0% outcomes) indicated results were sensitive to the discount rate, but the ICER remained below 20,000 EUR/QALY. CONCLUSIONS: Trastuzumab for the adjuvant treatment of HER2+ve EBC patients shows to be cost-effective from the Romanian National Health Insurance House perspective.