The cellobiose-fermenting yeast Brettanomyces clausenii was evaluated for the simultaneous saccharification and fermentation (SSF) of cellulose to ethanol Three cellulases were used in com- bination with Novo SP-122, Rut C-30, and Genencor 150L; and the results were compared to identical experiments with Saccharomyces cerevisiae. B. clause performed better than S. cerevisiae for cellulases low in e activity. The best performance for both stud- and straight saccharification was with the 150L cellulase, and a mixed culture e two yeasts ied gave better performance at 37°C than either yeast alone or straight saccharification at 50°C. Keywords: Brettanomyces lausenii, cellobiose, cellulose hydrolysis, enzymatic hydrolysis, simultaneous saccharification and fermentation