A metallic salt, hexahydratedaluminium chloride (AICI3), was shown to act as a potent inducer of phytoalexin synthesis in grapevines. AICI3 is the constituent of a new fungicide manufactured by Laboratoires Goemar and sold under the Synermix trademark. The efficiency of Synermix was tested for the control of grey mould in the vineyard, alone, or used in association with Iprodione. It has been shown that Synermix increased the efficiency of anti-Botrytis cinerea treatments. Results discussed herewith strongly supports the hypothesis that Synermix can act by stimulating host defence mechanisms in grapevines.