A technique has been examined for reducing the extent of crosslinking resulting from 1,1-di(t-butylperoxy)-3,3,5-trimethyleyclohexane (L-231) initiating melt grafting of vinyltriethoxysilane (VTEOS) onto poly(ethylene-co-vinyl acetate) (EVA). Using measurements of crosslink density and VTEOS conversion, a standard of selectivity for the EVA/VTEOS/L-231 system at 145 degreesC was defined and used to assess the influence of a range of additives (0.25 mol per mole VTEOS). The data indicated that compounds such as 4-nonene, N,N-dimethylaniline, and cumene improve reaction selectivity, whereas dodecane and cyclohexyl acetate have no effect. A strong correlation between the minimum C-H bond dissociation energy and the influence of a given compound is evident, suggesting that a labile C-H bond is the key element of an effective additive. A mechanism of additive function on the basis of hydrogen atom donation is proposed.