Xylose, a pentose indigestible to most yeasts, was converted to ethanol by a two-step isomerization and fermentation. HY zeolite was used to catalyze the isomerization of xylose, and the xylulose produced was directly used as the carbon source in ethanol fermentation. Zeolite catalysts offer pH compatibility with yeast fermentation and the ability to carry out isomerization at higher temperature where equilibrium xylulose concentration is higher. Initial rate studies indicate that xylose consumption follows pseudo-first-order kinetics, with a specific rate constant of 6.2 x 10(-4) L/solution/g zeolite/h.