Copolymers of butyl methacrylate (BMA) with 3-(methacryloylamino)-2-naphthoic acid (MANA) were neutralized with lithium methoxide, sodium methoxide, and cesium hydroxide. The counterion transfer from these copolymers to a BMA copolymer with [(2-(acryloylamino)prop-2-yl]methanesulfonic acid (APMS) was monitored by the fluorescence change in a stopped-flow apparatus in which solutions with equivalent concentrations of MANA and APMS residues were mixed. The half-life of this transport was 17 times smaller in dioxane than in toluene and increased with a decreasing size of the counterion. The apparent rate constant increased with the progress of the ion transfer, which was interpreted as due tb a decreasing ion-pair dimerization. The half-life of the process decreased much more rapidly with an increasing concentration of the interacting copolymers than expected for second-order kinetics. Addition of poly(butyl methacrylate) had no significant effect on the rate of counterion transfer from BMA/MANA to the BMA/APMS copolymer.