Combinations of Bis(trichloromethyl)sulfone, (Hexachlorodimethyl sulfone) and 1,2-Dibromo-2,4-dicyanobutane are shown to have synergistic antimicrobial properties. The synergistic compounds may be used together with a third microbiocide to enhance the compound’s effectiveness against a wide variety of bacteria, molds, and yeasts and other microorganisms.