OBJECTIVES: To analyze the purchase profile of antineoplastic drugs imatinib mesylate, trastuzumab and L-asparaginase by Brazilian federal agencies and the behavior of acquisitions in terms of quantities and prices.  METHODS: Exploratory study of purchases of imatinib mesylate 100 mg and 400 mg, trastuzumab 440mg vial and L-asparaginase 10.000UI vial performed between January/2004 and December/2013. Records were extracted from the Integrated General Services Administration federal database. Quantity, unit price, purchase date, type of purchase (regular or lawsuits) and federal buyer agency were analyzed. The annual weighted average unit price (WAUP) of each medicine was calculated. Current values were corrected by the National Consumer Price Index (IPCA) to December 2013.  RESULTS: The purchased quantities of imatinib and trastuzumab increased progressively each year and their WAUP showed a decreasing trend in all federal agencies. The Ministry of Health (MoH) was the main buyer. Reductions of WAUP were observed between 2009/2010 for imatinib even before the centralization of purchase by MoH in 2011. The incorporation of trastuzumab by the Brazilian Health System (SUS) and centralized purchases by the MoH (2012) resulted in a 57% reduction in WAUP. Prices and quantities of L-asparaginase varied between government agencies. The untoward 117% price rise in the centralized purchase by MoH (2013) may reflect shortages in the world market. Surprisingly there were no purchases related to health litigation for this medicine in the entire period.  CONCLUSIONS: Acquisitions presented increasing volumes of purchases and reductions in WAUP, with the exception of L-asparaginase. The centralization of procurement of imatinib and trastuzumab by MoH seems to justify the observed price reductions and reinforces the use of federal purchasing power in pricing negotiations to improve access to medicines in SUS.