Hydrodeoxygenation (HDO) reactions occur simultaneously with hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) during catalytic hydrotreatment of liquid fuels. Extensive research activities in the areas of HDS and HDN have been dictated by environmental concern to limit SO2 and NOX emissions. Different aspects of catalytic HDN and HDS have been reviewed frequently, most recently by Katzer and Sivasubramanian [1] and Furimsky [2], respectively. HDO has not attracted as much attention. This may be attributed to the very low amounts of oxygen found in conventional crudes, the main source of commercial fuels. Also, during HDO, the O is removed in an environmentally harmfulness form.