Hydrotreating of waste cooking oil (WCO) was studied as a process for biofuels production. The hydrotreatment temperature is the most dominant operating parameter which defines catalyst performance as well as catalyst life. In this analysis, a hydrotreating temperature range of 330-398 degrees C was explored via a series of five experiments (330, 350, 370, 385 and 398 degrees C). Several parameters were considered for evaluating the effect of temperature including product yields, conversion, selectivity (diesel and gasoline), heteroatom removal (sulfur, nitrogen and oxygen) and saturation of double bonds. For all experiments the same commercial hydrotreating catalyst was utilized, while the remaining operating parameters were constant (pressure = 1200 psig, LHSV = 1.0 h(-1), H(2)/oil ratio = 4000 scfb, liquid feed = 0.33 ml/min and gas feed = 0.4 scfh). It was observed that higher reactor temperatures are more attractive when gasoline production is of interest, while lower reaction temperatures are more suitable when diesel production is more important. (C) 2010 Elsevier Ltd. All rights reserved.