A series of amines were effective as additives for the control and rate enhancement of the living radical polymerization of methyl methacrylate (MMA) with RuCl2(PPh3)(3). On addition of n-Bu3N and n-Bu2NH, the polymerization with R-Cl/RuCl2(PPh3)(3) in toluene at 80 degreesC reached 90% conversion in 50 h and 94% in 20 h, respectively, while only 46% in 120 h without additives. The polymers obtained with n-Bu3N and n-Bu2NH had controlled molecular weights that increased in direct proportion to monomer conversion and narrow MWDs (M-W/M-n = 1.1-1.2). This is in sharp contrast to the uncontrolled molecular weights and broad MWDs (M-W/M-n = 1.7-2.0) obtained in the additive-free systems. Primary amines like n-BuNH2 and cyclic secondary amines like piperidine induced much faster polymerizations to result in broad MWDs (M-W/M-n = 1.7-1.8). Other additives such as pyridines, amides, alcohols, phenols, esters, and dimanies were not effective as additives for the ruthenium-catalyzed polymerizations. Interactions between the added amines and RuCl2(PPh3)(3) were observed by H-1 NMR analysis of the mixtures, where the amines coordinate to the ruthenium center and form highly active mononuclear ruthenium complexes.