The ability of lanthanide trisborohydrides Ln(BH4)3(THF)3 (Ln = La, Nd, and Sm) to produce either macrocyclic or linear poly(l-lactide) was established. The polymerization of l-lactide conducted under bulk conditions lead to the formation of cyclic polymers. When the same reaction was performed in the presence of benzyl alcohol as the transfer agent, it afforded alcohol-terminated linear polylactide in agreement with the occurrence of fully efficient transfer reactions to the alcohol.