Biodiesel is being proposed as an efficient replacement for fossil fuels. However, because of the difference in chemical compositions between biodiesel and fossil fuels, the resistance of polymeric materials to biodiesel may not be the same as that of fossil fuels. Thus, the aim of this work is to evaluate the resistance of different nitrile rubber (NBR) samples when in contact with biodiesel samples obtained separately from coconut oil and castor bean oil. The samples with lower acrylonitrile compositions (28 and 33%) exhibited low resistance to both pure biofuels. On the other hand, the mechanical properties of the NBR sample comprising 45% actylonitrile appeared unchanged even after immersion in biodiesel oils. (C) 2012 Elsevier Ltd. All rights reserved.