A study of the aqueous-phase free-radical chemistry is carried out to elucidate the reactions occurring between vinyl acetate and persulfate in the water phase; an understanding of this process is important for emulsion polymerizations involving vinyl acetate. Oligomeric species are identified using electrospray mass spectrometry. Reactions were performed between water-saturated solutions of vinyl acetate and persulfate at various concentrations, such that extensive oligomer formation occurred. These data, combined with simulations based on established models for the aqueous-phase events leading to radical entry into particles in emulsion polymerizations, suggest that the induced decomposition of persulfate seen at high initiator concentrations arises from transfer to initiator. Negligible induced decomposition of persulfate occurs at concentrations typically employed in emulsion polymerization (1-10 mM).