This paper reports on the influence of independent variables in the pulping of holm oak wood (Quercus ilex L.) [viz. temperature (135195 degrees C), cooking time (30-90 min) and soda concentration (10-20%)] on the yield, holocellulose content, a-cellulose content, brightness and viscosity of the resulting pulp. By using a central composite factorial design, equations relating each dependent variable to the different independent variables were derived that reproduced the experimental results for the dependent variables with errors less than 5-15% in all cases. The highest pulp yield (56.9%) was obtained with the lowest values of the operating variables. However, obtaining the optimum holocellulose content, a-cellulose content and viscosity (viz. 94.5%, 78.5% and 1395 ml/g, respectively) entailed using values of the independent variables above their mean levels. Also, ensuring optimal brightness (viz. 24.3%) required using higher temperatures and soda concentrations. A compromise that saves equipment immobilized capital and about 25% of soda is using a soda concentration of 15% at 195 degrees C for 30 min. The yield thus obtained differs by less than 29.5% from the highest level; also, the resulting holocellulose content, a-cellulose content and brightness differ by less than 12% from their respective optimum values. (c) 2007 Elsevier Ltd. All rights reserved.