The kinetic aspects and chain transfer processes of the stereospecific polymerization of butadiene initiated by catalyst systems consisting of nickel acetylacetonate and dialkyl alu-minium chloride have been studied．It has been shown that the rate of polymerization is first order with respect to both monomer and nickel acetylacetonate concentrations，but second order with respect to the diisobutylaluminium chloride concentration．Thus the poly-merization rate with diisobutylaluminuim chloride system is expressed as 一dM一dt =k[M][NiA2][Al(i—C4H9)2Cl]2 When diethylaluminium chloride instead of diisobutylaluminium chloride is used．the rate of polymerization is 1/2 order in diethylaluminium chloride concentration，that is， 一dM一dt =[M][NiA2][Al(C2H5)2Cl]1/2

On the basis of these results，a possible polymerization mechanism of these two systems is proposed．The overall activation energy of polymerization has been determined to be 8.0±0.5 kcal／mole for the NiA2一Al(i-C4H9)2Cl system，and 8．9±0．5 kcal／mole for the NiA2-Al(C2H5)2Cl system．Effects of monomer concentration，catalyst concentration，con-version，solvent，and additive compounds on the polymer molecular weight were also studi-ed．Variation of temperature from O一35°has no significant effect on the molecular weight of polybutadiene obtained，indicating that the difference in activation energy，Ep一Et，is small．Values of chain transfer and termination constants are also presented． It appears that transfer to nickel-containing compound is the main chain transfer reaction in this system．