Disclosed herein is a method for inhibiting and retarding the premature polymerization and the polymer growth of ethylenically unsaturated monomers comprising adding to said monomers an effective amount of at least one inhibitor that is a sulfonated nitrophenol of the formula: wherein: R1, R2, and R3 are independently selected from the group consisting of hydrogen, alkyl, NO2, and SO3H, provided that at least one of R1, R2, and R3 is NO2 and at least one of R1, R2, and R3 is SO3H. In a preferred embodiment, at least one additional inhibitor selected from the group consisting of nitroxyl compounds, nitrosoanilines, nitrophenols, amines, and mixtures thereof is also added.