Hydrodeoxygenation (HDO) of waste cooking oil and trapped grease over sulfide catalysts was examined to produce high quality transportation fuel from low-grade resources. The hydrodeoxygenation of waste oils was carried out in a high pressure batch reactor and a fixed bed flow reactor. Sulfide catalysts showed high HDO activity and all waste oils gave n-paraffins, isoparaffins and small amount of olefins. NiMo and NiW catalysts showed high and stable hydrogenation activity, whereas the deactivation of hydrogenation activity was observed using CoMo catalyst. NiW catalyst gave more hydrocarbons formed by decarboxylation or decarbonylation than NiMo and CoMo catalysts. The sulfur content in the product oil was low when catalytic activity showed constant. (C) 2010 Elsevier B. V. All rights reserved.