The inclusion of mineral acid, such as sulfuric, in certain monomer solutions, is shown to enhance the radiation grafting of styrene in methanol to a representative polyolefin, polypropylene. Thevariables affecting this acid enhancement on grafting efficiency have been studied and include type of solvent, concentration of monomer, presence of oxygen, radiation dose and dose rate and molarity of acid. The role of the solvent is particularly important. Grafting yields in the alcohols have been compared with analogous data obtained in other polar solvents such as dimethylformamide, dimethyl sulfoxide, acetone and dioxan. The present acid effects in radiation grafting to polypropylene are also compared with corresponding results previously obtained for acid-enhanced radiation grafting to the natural polymers, wool and cellulose. Extrapolation of the styrene acid effect to the radiation grafting of other monomers such as methyl methacrylate is considered.