In Mexico breast cancer reported an incidence of 13,939 cases and 5,217 mortality cases in 2008. Between 40-50% of those cases are diagnosed in stages III and IV. OBJECTIVES: The aim of this study was to assess a cost-effectiveness analysis for the use of fulvestrant 500mg as a therapy for postmenopausal women with locally advanced or metastatic breast cancer with ER+ receptor and prior progression on endocrine therapy, from Public Health Sector perspective in Mexico. METHODS: A cost-effectiveness analysis was performed using a Markov model with a time horizon of 1 and 5 years according to a prior economic evaluation and based on the results from CONFIRM study. Two cohorts of treatment were compared; Cohort A contemplates the addition of fulvestrant to the standard treatment and Cohort B the standard treatment. The effectiveness was measured as Life years Gained (LY). The use of resources was determined from the clinical practice in Mexico and costs were obtained from institutional sources. RESULTS: The ICER per LY for 1 year time horizon was $9,609 for Cohort A versus Cohort B. The fifth year implies an ICER of $6,581, being in both cases an ICER below the willingness to pay in Mexico (1 GDP: $10,000USD). CONCLUSIONS: Based on the findings the use of fulvestrant is a cost-effective strategy that provides a longer period of stable disease, an improvement in LY, diminish the use of chemotherapy and optimize institutional resources.