The present invention relates to combinations of imazalil, or a salt thereof, and silver compounds which provide an improved biocidal effect. More particularly, the present invention relates to compositions comprising a combination of imazalil, or a salt thereof, together with one or more silver salts selected from silver acetate, silver alginate, silver azide, silver citrate, silver lactate, silver nitrate, silver sulfate, silver chloride, silver thiocyanate, silver-sodium-hydrogen-zirconium phosphate, silver sulfadiazine, silver cyclohexanediacetic acid and disilver 2,5-dichloro-3,6-dihydroxy-2,5-cyclohexadiene-1,4-dione; in respective proportions to provide a synergistic biocidal effect. Other suitable silver components (II) are products that set silver free using technologies to make it gradually biologically available such as by ion exchange mechanisms such like using zirconium phosphate based ceramics as a reservoir, or silver provided in glass ceramics as reservoir or carrier, or silver provided with zeolites, silica gel or titanium dioxide as a reservoir or an inorganic derivative containing silver, incorporated into a plastic composition for the preparation of moulded, lacquered or painted products, such as an amino resin (e.g. urea-formaldehyde resin, melamine formaldehyde resin . . . ) or a thermoplastic (e.g. a polyester, polyethylene, polyacrylate, pvc . . . ), or provided as nano-silver particles typically with a particle size of 20-1000 nm. Compositions comprising these combinations are useful for the protection of any living or non-living material, such as crops, plants, fruits, seeds, objects made of wood, thatch or the like, biodegradable material and textiles against deterioration due to the action of microorganisms such as bacteria, fungi, yeasts, algae, and the like.