Under red light, disease development and infection hyphae formation by Botrytis cinerea were suppressed in broad bean, whereas, abundant lesion with many infection hyphae was produced in the dark. As a key factor for red light-induced resistance of broad bean, antifungal glycoprotein was isolated from inoculation droplets of B. cinerea spores. However, salicylic acid (SA) pre-treatment inhibited expression of red light-induced resistance dose-dependently, generating hydrogen peroxide (H₂O₂). Red light-induced resistance was recovered in the presence of a H₂O₂ scavenger, ascorbic acid or a NADPH oxidase inhibitor, diphenylene iodonium even in SA-pre-treated broad bean leaves. These results suggest that breakdown of red light-induced resistance in broad beans to B. cinerea is induced by membrane-mediated H₂O₂ generation. On the other hand, catalase activity in broad bean leaves was significantly enhanced under red light, but not in those pre-treated with SA and aminotriazole. We hypothesize that enhanced antioxidant enzyme catalase activity contributes to the inhibition of cell death in broad beans scavenging endogenous H₂O₂ generated by B. cinerea infection and to elicitor-dependent production of antifungal glycoprotein by living host cells; as a consequence, red light-induced resistance may be established. It is possible that an SA-dependent signaling pathway in broad beans is playing different roles in the plant-pathogen pathosystem.