Inoculation of different bean cultivars with Colletotrichum lindemuthianum race Beta results in a marked increase of Beta-1,3-glucanase and chitinase activities. The increase is much faster in incompatible than in compatible interactions. Induced Beta-1,3-glucanase (pI 9,5) differs from the constitutive Beta-1,3glucanase (pI 4,5) of healthy plants. The induced enzyme can partly degrade, in vitro, the cell walls of C. lindemuthianum. The possible role of these hydrolytic enzymes in plants defence is discussed.