Two monodisperse graft copolymers, poly(4-methylstyrene)-graft-poly(tert-butyl acrylate) [numb er-average molecular weight (M-n) = 37,500, weight-average molecular weight/number-average molecular weight (M-w/M-n) = 1.12] and polystyrene-graft-poly(tert-butyl acrylate) (M-n = 72,800, M-w/M-n = 1.12), were prepared by the atom transfer radical polymerization of tert-butyl acrylate catalyzed with Cu(I) halides. As macroinitiators, poly{(4-methylstyrene)-co-[(4-bromomethyl)styrene]} and poly{styrene-co-[4-(1-(2-bromopropionyloxy)ethyl)styrene]}, carrying 40% of the bromoalkyl functionalities along the chain, were used. The dependencies of molecular parameters on monomer conversion fulfilled die criteria for controlled polymerizations. In contrast, the dependencies of monomer conversion versus time were nonideal; possible causes were examined.