AbstractDetermination of the copolymerization reactivity ratios for the styrene/p‐sulfonamidostyrene and styrene/potassiump‐vinylbenzenesulfonate has given values ofr1= 0.24;r2= 1.07 andr1= 0;r2= 0.56, respectively. Values for the salt copolymerizations are subject to considerable variations, presumably due to adsorption of the monomer on the precipitating copolymers. The significance of these data in determining the distribution of the ionic groups in copolymers derived from these monomer pairs is discus