Esterification of corn and sunflower acid oils with straight- and branched-chain alcohols were conducted using lipase B from Candida antarctica (Novozym 435) in n-hexane. Sunflower acid oil consisted of 55.6% free fatty acids and 24.7% triacylglycerols, while the free fatty acids and triacylglycerols contents of corn acid oil were 75.3% and 8.6%, respectively. After 1.5 h of methanolysis of sunflower acid oil, the highest fatty acid methyl ester content (63.6%) was obtained at 40degreesC and the total fatty acid/methanol molar ratio was 1/1, using 15% enzyme based on acid oil weight. The conversion of both acid oils with straight- and branched-chain alcohols was not significantly affected by the chain length of the alcohols. However, the lowest fatty acid methyl ester content (50%) was obtained in the reaction of corn acid oil with methanol. Sunflower acid oil was converted to fatty acid esters using primer alcohols such as n-propanol, i- and n-butanol, n-amylalcohols, n-octanol, and a mixture of amylalcohol isomers, resulting in a fatty acid ester content of about 70% at 40degreesC.