Spores and infection structures such as germ tubes and appressoria of Magnaporthe oryzae, the fungus causing blast disease of wheat, produced an extracellular matrix (ECM) on the surfaces of host leaves during fungal differentiation. The chemical components and function of the ECM were studied to understand the pathological roles using two immunological techniques and ECM-digesting enzymes. The ECM was characterized by fibrous and amorphous materials, located in the spaces between fungal cell walls and plant cuticles. Immunohistochemical and immunoelectron microscopy suggested that ECM includes components positively reacted with antibodies of four animal cell adhesion factors (collagen VI, vitronectin, fibronectin and laminin) and an animal integrin α3. ECM, incubated on a cellulose membrane, was rapidly digested by matrix metalloproteinases (collagenase and gelatinase B), resulting in the detachment of most infection structures from membrane surfaces. Both ultrastructural observation and immunological responses showed that more ECM was located at the appressoria than at the spores and germ tubes. This result suggested that appressoria needed a powerful adhesion force for aggressive action of penetration pegs into plant cuticles.