A method for measuring cholesterol in low-density lipoprotein contained in a sample, which comprises reacting a sample with (i) a combination of cholesterol ester hydrolase and cholesterol oxidase or (ii) a combination of cholesterol ester hydrolase, an oxidized coenzyme and cholesterol dehydrogenase in the presence of: [a] a polyoxyethylene-polyoxyalkylene alkylaryl ether; [b] one or more surfactants selected from the group consisting of a polyoxyethylene-polyoxyalkylene copolymer, a polyoxyethylene alkenyl ether, a polyoxyethylene branched alkyl ether, and a polyoxyethylene-polyoxyalkylene branched alkyl ether; [c] one or more surfactants selected from the group consisting of a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium; and [d] a polyanion, and measuring a substance formed or consumed in the reaction.