The pathogenic fungus Gaeumannomyces graminis var. tritici secretes hydrolytic enzymes which degrade cellulosic polymers, when cultured on a medium containing carboxymethyl cellulose and Avicel. Two groups of enzymes were separated on a preparative isoelectrofocusing column. The first group contained an endoglucanase and β-glucosidase with acidic pIs of 4·0 and 5·6, respectively. The second group contained an endoglucanase and β-glucosidase with basic pIs of 9·3 and > 10, respectively. Each of the two enzyme groups released reducing sugars from carboxymethyl cellulose, hydroxyethyl cellulose and Avicel, but not from cotton. Degradation of filter paper and xylanase activity were detected with the acidic group only. A significant delay in the appearance of symptoms occurred when the inoculum was grown on a medium containing glucose. Cellulolytic activity was detected in inoculated wheat roots at the appearance of visual symptoms. Acidic and basic groups of endoglucanase and β-glucosidase were also obtained from inoculated wheat roots and appear to be similar to those isolated from the culture fluid.