Ethyl alpha-hydroxymethylacrylate was homopolymerized and copolymerized with methyl methacrylate in chlorobenzene and 1,4-dioxane solutions at 50 degrees C with 1.5 X 10(-2) mol/L 2,2'-azobisisobutyronitrile as an initiator and a global monomer concentration of 3.0 mol/L. The experiments showed differences in the calculated values of the monomer reactivity ratios in both solvents. The kinetic behavior was analyzed in terms of the implicit penultimate effect and the radical reactivity ratios. All the parameters were examined with respect to the aggregation ability of the ethyl a-hydroxymethylacrylate monomer. (c) 2005 Wiley Periodicals, Inc.