The copolymer prepared by copolymerizing styrene and maleic anhydride was imidized with N,N’-dimethylaminopropyl amine. The styrene-N,N’-dimethylaminopropyl maleimide (SDMAPM) copolymer obtained was then reacted with propane sultone to yield a styrene-[N,N’-dimethyl(maleimidopropyl)ammonium propane sulfonate] (SDMMAPS) copolymer. The cloud point and intrinsic viscosity of this ampholytic SDMMAPS copolymer were determined in aqueous salt solutions. The effects of counter ions on the cloud point and intrinsic viscosity of SDMMAPS were similar to their effects on these properties of other zwitterionic poly(sulfobetaine)s. The Huggins constants for SDMMAPS in aqueous salt solutions, however, were quite different than those of other sulfobetaine homopolymers, such as poly[N,N’-dimethyl(acrylamidopropyl) ammonium propane sulfonate], [poly(DMAAPS]. The value of the constant was negative and increased as the intrinsic viscosity and salt concentration increased. This phenomenon is mainly attributed to the presence of the styrene segment, a hydrophobic group, in the SDMMAPS copolymer.