OBJECTIVES: In Brazil, health insurance companies (HIC) must, according to the law, offer coverage for intravenous (IVChem) antineoplastic drugs. The obligation to pay for oral drugs (OChem) was effective only after January 2014. Our goal was to evaluate the incremental costs and budgetary impact of the incorporation of OChem, using real world data, from the private payers’ perspective.  METHODS: During one year (Jun 2012-mai 2013) we prospectively collected data on chemotherapy usage in 25 HIC, with a population of 3 million people from different regions in Brazil. First we calculated the costs of IVChem actually used. After that, we identified which patients would have formal indication for OChem either as a substitutive treatment or in association with IVChem. Then, we calculated the costs associated with this intervention. Later, the budgetary impact of using OChem for the eligible patients was calculated. Only drug acquisition costs were taken into account. We analyzed two scenarios: one with a total substitution of IVChem for OChem, when OChen treatment was less expensive than IVChem and another, using a “worst case scenario” approach, were OChem was used only in cases where it added costs.  RESULTS: During the one-year period, 2,104 patients that received intravenous chemotherapy also had formal indication to receive OChem. If OChem had been used, in a rational protocol-based manner, there would have been an economy of R$ 0,10 (US$ 0,42) per HIC user per month. In the worst-case scenario, the incremental cost would be an additional R$ 0,39 (US$ 0,16) per HIC user per month.  CONCLUSIONS: The budgetary impact secondary to OChem adoption may vary from decreasing costs to increasing them; depending on how they are used and to which patient they are prescribed. HIC should pay close attention to the profile of use of OChem in order to avoid unnecessary costs.