The copolymerization of N-vinylpyrrolidone (NVP) with ethyl methacrylate (EMA) was studied in the presence of ZnCl9 as complexing agent. It was found that the monomer reacti- vity ratio of NVP (rj decreases since for EMA (r2) increases with increasing the molar content of ZnCl2 in the reaction medium. The variation of and r2 from the characteristic poiut of view was explained in terms of the effects of ZnCl2 on the reactivity of ethyl metlıacryslate and poly (ethyl methacrylate) radical. Consequently, the copolymerization reaction can be taken as a mul- ticomponent System where nine reactions have to be taken into consideration.