A silica gel support system for the copper bromide-hexamethyltriethylenetetramine (HMTETA) complex was successfully developed for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in toluene. The supported complex mediated a living polymerization of MMA, yielding polymers with controlled molecular weights and narrow molecular weight distributions. The MMA concentration had significant influence on the polymerization behavior. At 33% MMA concentration, the polymerization catalyzed by CuBr-HMTETA/silica gel followed typical first-order kinetics with respect to the monomer. But at 50% MMA, the polymerization significantly deviated from the first-order kinetics after the MMA conversion reached 30%. The supported catalysts were recycled for second and third uses. The recycled catalysts remained 80% active in the second use and 50% in the third use relative to their initial activity. The recycled catalysts had even better controllability over the polymerization. The molecular weights of PMMA produced agreed with the predicted values, and the polydispersities were less than 1.2.