OBJECTIVES: The use of Trastuzumab (T) for the adjuvant treatment of breast cancer patients (BCP) has been tested in clinical trials. Our goal is to perform a health technology evaluation in order to stablish if the scientific evidences are strong enough to support the use of T and to compare its cost-effectiveness ratio (CER) with other treatments covered by the public sector in Brazil. METHODS: We performed a literature search, looking for randomized controlled clinical trials (RCTs), systematic reviews (SR), guidelines, pharmacoeconomic analysis and endorsements from regulatory agencies on the use of T for BCP. RESULTS: We found five RCTs, three SR, six guidelines / health technology assessments and three endorsements from regulatory agencies. Four RCTs tested Trastuzumab 2 mg/kg/week or 6 mg/kg/ every 3 weeks during one year,  in patients with tumors >= 1cm. All of these showed a 50% reduction on risk of relapse and a 40% reduction in death risk. SR confirmed these findings. The only study that did not show a survival gain, used T for only nine weeks. Guidelines and regulatory agencies recomend the use of T for one year. On the pharmacoeconomic perspective, T has a CER  similar or better than other procedures covered by the public sector in Brazil, such as heart transplant, tacrolimus for kidney transplantation, ribavirin plus peg-interferon for C hepatitis and bone marrow transplant. These procedures have a CER betwen US$35,000 and US$45,000 / QALY (or above). The CER of adjuvant T is around US$20,000/QALY. CONCLUSIONS: Trastuzumab is indicated for the adjuvant treatment of BCP, and must be considered as standard treatment for these patients. Also, from a pharmacoeconomic point of view, it’s CER is similiar to other medical interventions covered by the Brazilian healthcare public system.