The growth of corn-based ethanol production and soybean-based bio-diesel production following the increase in the oil prices have significantly affect the world agricultural grain productions and its prices. The main purpose of this paper is to investigate the relationships between the crude oil price and the global grain prices for corn, soybean, and wheat The empirical results show that the change in each grain price is significantly influenced by the changes in the crude oil price and other grain prices during the period extending from the 3rd week in 2005 to the 20th week in 2008 which implies that grain commodities are competing with the derived demand for bio-fuels by using soybean or corn to produce ethanol or bio-diesel during the period of higher crude oil prices in these recent years The subsidy policies in relation to the bio-fuel industries in some nations engaging in bio-fuel production should be considered to avoid the consequences resulting from high oil prices. (C) 2010 Elsevier Ltd All rights reserved.