The hyphal wall components (HWC) from Phytopthora capsici, P. infestans and P. nicotianae var. nicotinae, which caused the hypersensitive cell death of suspension-cultured cells of sweet pepper ( Capsicum frutescenceL.), tomato ( Lycopersicon esculentum Mill.) and tobacco ( Nicotiana tabacumL.), enhanced the luminol-mediated chemiluminescence in suspensio-cultured cells of each plant within several minutes after treatment with HWC in a species-nonspecific manner. HWC-induced chemiluminescence in suspension-cultured cells was enhanced by incubation with superoxide dismututase but was significanyly inhibited by pretreatment with catalase or, the O 2 −scavenger, Tiron. Similarly, Tirom or water-soluble glucans (WSG) from respective species of Phytophthora suppressed both the HWC-induced chemilunescence and hypersensitive cell death specific only to its own host. These results suggested that Phytophthora spp. may produce suppressor-gluncans which inhibit the activation of O 2 − generation responsible for triggering hypersensitive cell death in the respective Solanaceous host plants and permit the establishment of a compatible interaction.