The glucose analog 2-deoxyglucose (2-DOG) has been used to obtain mutants derepressed for pentose metabolism. Some researchers have used 2-DOG alone whereas others have used it in the presence of a glucose-repressible carbon source. We examined both methods and screened mutant strains for improved use of xylose in the presence of glucose. Pichia stipitis mutants selected for growth on D-xylose in the presence of 2-DOG used xylose from a 1:1 glucose:xylose mixture more rapidly than did their parents. One of these mutants, FPL-DX26, completely consumed xylose in the presence of glucose and produced 33 g/L ethanol in 45 h from 80 g/L of this sugar mixture. Mutants selected for growth on 2-DOG alone did not show significant improvement. Selection for growth on D-xylose in the presence of 2-DOG has been useful in developing parental strains for further genetic manipulation