Waste vegetable oils and their mixture with RBD palm oil are used to obtain ethylic esters with the purpose of evaluating the influence of treatment of waste vegetable oils, the use of industrial anhydrous ethanol in different molar ratios and the use of KOH and CH3 ONa as catalyst on the yield of reaction. The best results are obtained using a mixture 80:20 of RBD palm oil and waste vegetable oil without treatment, 9:1 molar ratio of ethanol:oil and 0,5% w. CH3 ONa as catalyst to 60 °C. The use of KOH as catalyst provides lower yields of reaction; however their behaviour is less influenced by changes in the quality of the raw materials