OBJECTIVES: In Brazil, health insurance plans (HI) must pay for anticancer  intravenous (IV) chemotherapy (CHEMO) but not for those taken by mouth (PO). Erlotinib (E) is a PO CHEMO used to treat lung cancer 2nd or 3rd line. Our aim was to establish the budgetary impact of the adoption of E, when compared to the IV competitors docetaxel (D) and pemetrexed (P) for the HI in Brazil. METHODS: We searched Evidencias Database for patients eligible for the use of E, in the year of 2008. This database has information from 2 million of users of 14 HI. Then, we calculated the costs of the IV chemo actually used. A simulation of the costs if E were adopted was carried out.  Many different sensitivity analyses were performed, according to the line of treatment in which E was administered and the proportion changing from IV to the PO option. RESULTS: We found 285 records of patients that were suitable for the use of E. The cost of IV CHEMO was US$2,293,000. If E replaced the treatment for all patients, the cost would be reduced to US$1,067,000, resulting in a economy of US$1,222,000 (54%) of the total. If instead of replacing the IV option, E was used as an additional line of treatment, an increase of  US$635,000 in total costs would occur. In a sensitivity analysis, that can reflect the practice, where 50% of the patients would receive E instead of P or D in 2nd line, and 30% would receive E in 3rd line, the adoption of E would result in an economy of US$295,000. CONCLUSIONS: The adoption of E for the treatment of lung cancer in Brazil can be cost-saving  for HI.