A series of acidic acrylate polymers have been made, by group transfer polymerization, with narrowly defined molecular weight and structure. Both block and random copolymers, with different proportions of carboxylate groups to butyl ester groups, have been tested as inhibitors for the crystallization of calcium oxalate. The degree of inhibition is measured as the reduction in initial crystallization rate, determined by conductivity of the crystallizing solution. The inhibition increases with acid content of the polymer but is essentially unaffected by polymer architecture. These results are interpreted in terms of theories of polymer binding to solid surfaces. Changing the butyl ester to a more hydrophilic ester also made little difference. Acrylates were much more effective than the equivalent methacrylates. Molecular modelling suggests that there was no difference in ion binding between these two families of polycarboxylates. The higher inhibition efficiency is believed to arise from the closer chain packing on the crystal surface.