Mold preventing action of the following 13 compounds were tested against soy sauce: Thymol, p-nitrosothymol, p-nitrothymol, p-aminothymol hydrochloride, o-nitroso-m-cresol, m-nitroso-o-cresol, p-nitrosophenol, 2-nitroresorcinol, 4-nitroresorcinol, 2-aminoresorcinol hydrochloride, 4-aminoresorcinol hydrochloride, o-chloro-p-aminobenzoic acid and p-quinone dichloroimide. In contrast to the complete prevention of molding in a 5-day test period by propyl p-hydroxybenzoate, used as control, in 0.01% concentration, p-nitrothymol, in ca. 0.003% concentration, p-quinone dichloroimide, in ca. 0.005% concentration, and thymol, in ca. 0.007% concentration, were able to prevent molding during the same period. Other compounds were found to have no action of preventing molding of soy sauce.