The higher feedstock and processing costs for biodiesel production can be reduced by applying reactive distillation (RD) in transesterification process. The effects of reboiler temperature, amount of KOH catalyst, methanol to oil molar ratio and residence time on the methyl ester purity were determined by using a simple laboratory-scale RD packed column. The results indicated that from the empty column, the system reached the steady state in 8 h. Too high reboiler temperature and the amount of catalyst introduce more soap from saponification in the process. The optimal operating condition is at a reboiler temperature 90 degrees C, a methanol to oil molar ratio of 4.5:1.0, KOH of 1 wt.% respect to oil and 5 min of residence time in the column. This condition requires the fresh feed methanol 25% lower than in the conventional process and produces 92.27% methyl ester purity. Therefore this RD column can be applied in small or medium biodiesel enterprise. (C) 2013 Elsevier B.V. All rights reserved.