The invention relates to a storage stable biocide composition comprising the following components: (a) 2wt.% - 20wt.% of one or more isothiazolinones selected from the group consisting of methylisothiazolin-3-οne (MIT), 1,2-benzisothiazolin-3-οne (BIT) and N-methyl-1,2-benzisothiazolin-3-one (M-BIT), (b) 65wt.% - 97wt.-% of at least one biocide selected from the group of phenoxyethanol, phenetyl alcohol and phenylpropanol and (c) 1wt.% - 15wt.% water. The invention also relates to the use of the composition for protecting technical materials from attack and/or destruction by microorganisms.
