The objective of this work is to study the effects of reaction temperature, reaction time and ethanol percentage on the pretreatment of oil palm fronds (OPF) using ethanolic hot compressed water (EHCW) to enhance sugar recovery in enzymatic hydrolysis. A central composite rotatable design was used to optimize the pretreatment process conditions. All variables (individual and interactive) were found to affect glucose recovery significantly. A quadratic polynomial equation was modelled for glucose recovery by multiple regression analysis using response surface methodology (RSM). Using a 10 bar pressurized reactor, the optimum conditions for pretreatment of OPF were obtained at 180 degrees C, 42 min and EtOH wt.% of 26.4%. At the optimum conditions, the predicted glucose recovery was 88.48%. Experimental verification of the optimum conditions gave glucose recovery well within the estimated value of the model. (C) 2010 Elsevier B.V. All rights reserved.