Suspension cell cultures of grapevine (Vitis vinifera, cv. Monastrell) treated with an elicitor (cellulase, Onozuka R-10) from Trichoderma viride showed a hypersensitive-like response. This was characterized by cell plasmolysis and was accompanied by localized cell death, which was concomitant with cell culture browning, itself probably due to an activation of oxidative phenolic metabolism driven by a large increase in endogenous levels of H2O2. In addition to these responses, the treatment of cell cultures with the elicitor produced an increase in amounts of benzoic acid and of resveratrol, the latter a potent phytoalexin of grapevines. This hypersensitive-like response was specific since none of the above responses was obtained with other cell wall-degrading enzymes from several sources, or with inocula of either mycelial extracts or culture filtrates of Botrytis cinerea. These results are discussed in the light of a disease-resistance reaction induced in grapevine cells by a product of T. viride, a fungal agent characterized by its effective biocontrol of Botrytis cinerea, the causal agent of grey mould in grapevines.