Typically a Ziegler-Natta catalyst formulation includes the use of alkyl aluminum compounds and this investigation involves the substitution of triethyl aluminum (TEAL) with n-BuLi. It was found that this lithium compound, used as first co-activator, produced polyethylene at rates high enough for solution polymerization technology. Catalyst activity and molecular weight data were collected from a lab-scale continuous polymerization reactor at 150, 170 and 190oC. A balance between n-BuLi and a second alkyl aluminum compound (AA-2), used as second co-activator in the catalyst formulation, enabled the catalyst to achieve a performance (catalyst activity and polymer molecular weight) similar to that obtained with TEAL. It is proposed that the optimum balance between these two compounds is related to the difference in the reducing power of n-BuLi and AA-2, and one of the chain transfer reactions is to AA-2.