An extracellular beta-1,3-glucanase with antifungal properties was secreted by the novel mycoparasite, Periconia byssoides. The glucanase has a molecular mass of 35 kDa estimated by SDS-PAGE. Its optimum activity was at pH 6.0 and 50 degrees C (over 2 h). The purified beta-1,3-glucanase was capable of degrading cell walls, and inhibiting mycelia growth and spore germination of plant pathogenic fungi including Fulvia fulva, Fusarium sp. and Rhizoctonia solani. The N-terminal amino acid residues of the purified beta-1,3-glucanase are LKNGGPSFGA, which do not have any homology with previously described glucanases, suggesting it may be a novel member of the fungal beta-1,3-glucanases.