The effects of the three main enzymes involved in cellulose saccharification, namely cellobiohydrolase, carboxymethylcellulase and beta-glucosidase, on the direct conversion of cellulose to ethanol by Fusarium oxysporum F3 were investigated. Ethanol production was not affected when the activity of the former two enzymes was varied within a wide range. By contrast, beta-glucosidase markedly affected ethanol production showing an optimum level of 0.7-0.8 unit/ml growth medium. A significant decrease of cellulose bioconversion time to ethanol was obtained when beta-glucosidase activity was adjusted to this optimal level at the beginning of the fermentation process.