A stable, low VOC, low viscosity biocide formulation comprising an effective amount of at least one biocide, 1,2-benzisothiazolin-3-one (BIT), and a polyglycol liquid carrier of formula (I): R-O-(AO)-O-R1, wherein n is 4-25, R and R' are hydrogen, C-C alkyl groups, O=C-CH group, or O=C-CH group, and AO is a) CHCHO, or b) CHCHO /CHCHMe-O block or random copolymer; with proviso that when R and R' are both hydrogen, AO is a block or random copolymer. A method of making such a formulation.