This paper presents the study of the transesterification of palm oil via heterogeneous process using montmorillonite KSF as heterogeneous catalyst. This study was carried out using a design of experiment (DOE), specifically response surface methodology (RSM) based on four-variable central composite design (CCD) with a (alpha) = 2. The transesterification process variables were reaction temperature, x(1) (50-190 degrees C), reaction period, x(2) (60-300 min), methanol/oil ratio, x(3) (4-12 mol mol(-1)) and amount of catalyst, x(4) (1-5 wt%). It was found that the yield of palm oil fatty acid methyl esters (FAME) could reach up to 79.6% using the following reaction conditions: reaction temperature of 190 degrees C, reaction period at 180 min, ratio of methanol/oil at 8:1 mol mol(-1) and amount of catalyst at 3%. (C) 2008 Elsevier Ltd. All rights reserved.