With the aim of understanding the contribution of enzymes to the cost of lignocellulosic biofuels, we constructed a techno‐economic model for the production of fungal cellulases. We found that the cost of producing enzymes was much higher than that commonly assumed in the literature. For example, the cost contribution of enzymes to ethanol produced by the conversion of corn stover was found to be $0.68/gal if the sugars in the biomass could be converted at maximum theoretical yields, and $1.47/gal if the yields were based on saccharification and fermentation yields that have been previously reported in the scientific literature. We performed a sensitivity analysis to study the effect of feedstock prices and fermentation times on the cost contribution of enzymes to ethanol price. We conclude that a significant effort is still required to lower the contribution of enzymes to biofuel production costs. Biotechnol. Bioeng. 2012; 109:1083–1087. © 2011 Wiley Periodicals, Inc. The cost contribution of enzymes to the production of lignocellulosic biofuels has been widely debated. By modeling the production of cellulolytic enzymes and analyzing the technical and economic performance of the process, the authors estimated their cost. Furthermore, using information about enzyme use in typical biorefinery processes, the authors were able to determine the contribution of enzymes to the total cost of production of lignocellulosic ethanol. The authors concluded that this contribution is much higher than estimates given in the literature.