A substantial amount of fatty acid mixture residue is generated in the palm oil-based oleochemical industries in Malaysia. The recovery of fatty acids residue is difficult and not economical; therefore, its alternative usage is explored. The fatty acid mixture can be converted to liquid hydrocarbon fuel and chemicals using catalytic technology. In the present study, the catalytic cracking of fatty acid mixture residue to liquid hydrocarbon fuel was studied over HZSM-5 catalyst in a fixed-bed microreactor at atmospheric pressure. The effect of reaction temperature (400-450degreesC), fatty acid/catalyst ratio (6-10) and weight hourly space velocity (2.5-4.5 h(-1)) was studied over the yield of liquid hydrocarbon fuel. Design of experiments was used to study the effect of operating variables over conversion of fatty acid mixture and yield of hydrocarbon fuel. The response surface methodology was used to determine the optimum value of the operating variables for maximum conversion of fatty acid mixture and yield of gasoline fraction in the liquid product obtained. (C) 2004 Elsevier Ltd. All rights reserved.