A method has been developed to determine the free glycerol content in esters derived from vegetable oils. After extraction of glycerol, its measurement in small quantities in biofuels (methyl or ethyl esters) is possible by high-pressure liquid chromatography combined with pulsed amperometric detection, HPLC-PAD. The method has proved to be simple, rapid and accurate. The limit of detection is 1 microg/g.