The production of enzymes of the cellulase complex by the fungus Neurospora crassa on milled and sieved wheat straw was studied. The effects of straw concentration, temperature, and initial pH on the production of the beta-glucosidase, exoglucanase, and endoglucanase activities, as well as extracellular and mycelial protein, were observed. With an initial pH value of 6.5 and a temperature of 30 degrees C, a straw concentration of 5% yielded the higher activities for all the enzymes. Two maxima were observed both for beta-glucosidase and endoglucanase, while the exoglucanase activity was constant from the end of the exponential phase. When a protease inhibitor was added, the production of beta-glucosidase was increasing without fluctuations. When the temperature was 25 degrees C, the enzymes production was lower, whereas the mycelial protein value was higher. Changes in the initial pH, lowering or raising it, lowered the enzymes production, but favored fungus growth.