OBJECTIVES: This study aims to assess the long-term cost-effectiveness of Trastuzumab in the adjuvant treatment of HER2-positive breast caner. METHODS: 1) A Markov model was established to simulate the natural development of breast cancer based HERA (HERceptin Adjuvant) trial, estimate direct medical expenditures and disease progression over a lifetime perspective with annual transition cycles, and evaluate the cost-effectiveness of one-year adjuvant trastuzumab following standard chemotherapy. 2) 28 famous clinicians in the specialty were investigated to inquire the proportion of the average follow-up patients who take outpatient visit and hospitalization and the frequency of medical care utilization including examination, lab tests, all kinds of treatments (surgery, hormonal therapy, chemotherapy, radiotherapy, special interventions). All clinicians were required to give the second estimate based on the feedback of the average of every item derived from the first round survey. The average of every item based on the second round survey was calculated and employed to measure the annual medical expenditure burden under different health states according to the fee schedule of medical services and pharmaceuticals related in Beijing, Shanghai and Guangzhou cities. 3) A discounting rate at 3% was used to discount medical expenditure happened at different years. One-way sensitivity analysis was carried out to understand the key drivers and general sensitivity of the model. Selected parameters were varied through a specific range and the impact on the cost-effectiveness ratio. RESULTS: The results showed that the utilization of trastuzumab in the adjuvant treatment in early breast cancer can prolong 2.87 life years, compared to standard adjuvant chemotherapy, and the incremental cost for an additional life year ranged from 50,239 to 54,736 yuan RMB (US$7,076~7,709), according to the fee schedule and pharmaceutical prices in Beijing, Shanghai and Guangzhou cities. If measured by the quality of life, the incremental cost ranged from 50,978 to 55,541 yuan RMB (US$7,180~7,823) per QALY. CONCLUSIONS: Trastuzumab utilized in the adjuvant treatment of HER2-positive breast cancer in developed urban China is cost effective, according to GDP per capita as threshold of economic evaluation.