Copolymers of methyl methacrylate and n-butyl acrylate were prepared using atom transfer radical polymerization catalyzed by CuBr/4,4'-di(5-nonyl)-2,2'-bipyridine (dNbpy), CuBr/N,N,N',N " ,N " -pentamethyldiethylenetriamine (PMDETA), and CuBr/tris[2-(dimethylamino)ethyl]amine (Me6TREN). Point estimates and 95% joint confidence intervals of the reactivity ratios were calculated for the copolymerizations catalyzed by CuBr/dNbpy (r(MMA) = 2.52, r(BA) = 0.265) and those catalyzed by CuBr/PMDETA (r(MMA) = 3.15, r(BA) = 0.37) using previously described least-squares calculations. Semilogarithimic plots of monomer conversion vs time were nearly linear. Plots of M-n vs monomer conversion were linear, and polydispersity decreased with increasing monomer conversion. Copolymerizations were simulated using Predici 5.3.2 in order to better understand the experimentally observed results.