An homogeneous reaction process using acetone as a co-solvent for the transesterification of vegetable oils with methanol in the presence of potassium hydroxide catalyst has been developed. The effects of the main parameters, such as the amounts of acetone and KOH, the molar ratio of methanol to oil and the reaction temperature, on fatty acid methyl esters (FAME) yield were investigated. The optimal conditions were: 25 wt.% acetone and 1.0 wt.% KOH catalyst in oil; a molar ratio of methanol to oil of 4.5: 1; and a reaction temperature of 25 degrees C. Under these conditions, the conversion of vegetable oil to FAME exceeded 98% after 30 min. This method was applied to produce biodiesel fuel (BDF) from waste cooking oil (WCO), canola, catfish and Jatropha curcas oils, with the main product quality factors satisfying the JIS 2390 BDF standards. (C) 2012 Elsevier Ltd. All rights reserved.