Aims: It is evaluated the effectiveness of the combined action of two highly thermostable enzymes for the hydrolysis of xylans at high temperature in order to produce b-xylose. Methods and Results: Xylans from different sources were hydrolyzed at high degree at 70 degrees C by co-action of a xylanase from the thermophilic bacterium Anoxybacillus flavithermus BC and the novel beta-xylosidase/alpha-arabinosidase from the hyperthermophilic crenarchaeon Sulfolobus solfataricus O alpha. Beechwood xylan was the best substrate among the xylans tested giving, by incubation only with xylanase, 32-8 % hydrolysis after 4 h. The addition of the beta-xylosidase/ a-arabinosidase significantly improved the rate of hydrolysis, yielding 63-6% conversion after 4 h incubation, and the main sugar identified was xylose. Conclusions: This study demonstrates that a significant degree of xylan degradation was reached at high temperature by co-action of the two enzymes. Xylose was obtained as a final product in considerable yield. Significance and Impact of the Study: Although the xylan represents the second most abundant polysaccharide in nature, it still doesn't have significant utilization for the difficulties encountered in its hydrolysis. Its successful hydrolysis to xylose in only one stage process could make of it a cheap sugar source and could have an enormous economic potential for the conversion of plant biomass into fuels and chemicals.