An antimicrobial composition comprising at least two quaternary ammonium compounds selected from: (i) a quaternary ammonium compound having the formula: A4-nSi(R—NHaR1bZ)n and (ii) a quaternary ammonium compound having the formula: NHcR1dZ wherein in each of the at least two quaternary ammonium compounds A, R, R1, a, Z and n are independently selected, and: A is a member selected from the group consisting of alkoxy radicals, alkylether alkoxy radicals, and alkyl radicals; R is a divalent hydrocarbon radical; each R1 is independently a member selected from the group consisting of benzyl, alkyl radicals, alkyl ether hydrocarbon radicals, hydroxyl-containing alkyl radicals, and nitrogen-containing hydrocarbon radicals; Z is a member selected from the group consisting of chloride, bromide, iodide, tosylate, hydroxide, sulfate and phosphate; a is 0, 1 or 2, b is 1, 2 or 3, and the sum of a and b is 3; c is 0, 1, 2 or 3, d is 1, 2, 3 or 4, and the sum of c and d is 4; and n is 1, 2 or 3; and wherein the composition comprises at least two quaternary ammonium compounds of formula (i). A method of making an anti-microbial composition, and a method of reducing the number of micro-organisms on a surface, are disclosed.