The alternating copolymerization of chloroprene (CP) with methyl acrylate (MA) in the presence of ethyl aluminium sesquichloride (AlEt1.5 Cl1.5) and initiator Mn2(CO)10/CCl4 has been studied.The rate of eoplymerization is proportional to [MA…al]1/2

where MA…al represents the MA-AlEt1.5Cl1.5 complex and 9 is the rate of initiation. All the kinetic data are consistent with the cross-propagation mechanism of alternating copolymerization. The propagation process -CP + MA is markedly accelerated by Al Et1.5Cl1.5

com-pared with 11.1 and 0.078 without it. Chain transfer to CBr4has been observed and the apropriate kenetic parame-ters evaluated.