Eucalyptus globulus wood hydrolysates were concentrated by vacuum evaporation to increase their xylose contents, treated with activated charcoal, supplemented with nutrients and used as culture media for xylitol production by Debaryomyces hansenii NRRL Y-7426. The susceptibility of hydrolysates to fermentation was strongly dependent on the initial cell concentration : media containing 58-78 g xylose/l were hardly consumed in batch experiments starting with 16 g cells/l, whereas 39-41 g xylitol/l were achieved in fermentations carried out with similar concentration of the carbon source and initial cell concentrations of 50-80 g/l)..