The mass yield of a base-catalyzed soybean oil methanolysis was maximized to 87.09 (wt/wt%) through response surface methodology with five levels and four factors. An economy of 33% methanol, 33% sodium hydroxide, and 50% reaction time was achieved in relation to other optimization researches which were previously reported in the literature. The obtained biodiesel attends the ANP quality standards for the following items: ester amount wt%, free glycerol (wt/wt%), mono-, di-, and triacylglycerols (wt/wt%), and total glycerol (wt/wt%). (C) 2013 Elsevier Ltd. All rights reserved.