The ternary neodymium-based catalyst for the polymerization of 1,3-butadiene, Nd(versatate)(3)/Ali-Bu(2)H/tert-butyl chloride, has been examined with respect to the effects of a range of alkylaluminums and alkylaluminum chlorides. Using either pre-formed or in situ catalysts, observations pertaining to catalyst activity and physical state and the characteristics of the final polymer are discussed. The catalyst activity series with the type of alkylaluminum was found to be : Aln-Pr-3 much greater than Aln-Dodec(3) = Aln-Oct(3) = Aln-Hex(3) > Ali-Bu(2)H congruent to Ali-Bu(3) > AlEt(3) much greater than AlMe(3). Polybutadiene cis content was found to vary with the type of alkylaluminum used. Pre-formed catalysts using methylaluminum chlorides as chloride source were found to be the most active; AlMe(2)Cl chloride gave the highest activity. The activity of in situ catalysts prepared using alkylaluminum chlorides was found to be independent of alkylaluminum chloride structure. Polybutadiene prepared using catalysts based on different alkylaluminums and alkylaluminum chlorides was found to decrease in cis content with conversion.