Abstract: The use of hydroxystilbene compounds of formula wherein A is a radical of formula  or a radical of formula  and R1, R2, R3, R4 and R5 are each independently of the others hydrogen, halogen, hydroxy, C1-C16alkyl, C1-C16alkoxy, phenyl; C1-C3phenylalkyl; C6-C10aryloxy, amino, mono-C1-C5alkylamino, di-C1-C5alkylamino, or —NO2; as microbicidal active ingredients is described. The compounds exhibit a pronounced action against pathogenic gram-positive and gram-negative bacteria, and also against yeasts and moulds. They are therefore suitable for the antimicrobial treatment, especially the preservation and disinfection, of surfaces.