Copper-mediated ATRP in protic solvents is characterized by inefficient deactivation due to reversible dissociation of a halide ligand from the ATRP deactivator (CuLnX)-L-II (L = bipyridine or another amine or imine, X = Br, Cl), which may be followed by competitive coordination of solvent to the Cu-II center. This process is strongly solvent-dependent and leads to fast and often poorly controlled polymerizations. The loss of a halide ligand from the deactivator in ATRP reactions in the presence of water or other coordinating compounds can be suppressed by the addition of halide salts allowing the regeneration of the dissociated Cu-II-X species and, therefore, increasing the deactivation rate. The deactivation step in ATRP, which is of primary importance for control over the polymerization, can also be accelerated by employing a catalyst system initially containing a sufficiently large amount of Cu-II-halide complex. These approaches are illustrated by conducting the controlled radical polymerization of 2-hydroxyethyl methacrylate, 2-(N,N-dimethylamino)ethyl methacrylate, 2-(trimethylammonio)ethyl methacrylate trifluoromethanesulfonate, and 2-(dimethylethylammonio)ethyl methacrylate bromide.