The radical copolymerizations of chloroprene (CP) and a-cyanoethyl acrylate (CEA) were carried out in toluene at 45 degrees C in moisture free atmosphere by use of dry nitrogen. Microstructures in the copolymers have been examined by H-1 and C-13 nuclear magnetic resonance and Fourier transform infra-red spectroscopy. They showed that the copolymer, whose composition ratio was nearly CP/CEA = 1/1(mol), possessed predominantly(CP-CEA)-repeating unit in which CP had the 1,4 unit. A reaction mechanism by way of Diels-Alder intermediate was discussed for this regular copolymerization.